MAR 141 




DESCRIPTIVE 
GENERAL CHEMISTRY 



A TEXT BOOK FOR SHORT COURSE 



BY 



S. E.f TILLMAN 

Professor of Chemistry, Mineralogy and Geology 
United States Military Academy 




WEST POINT, N. Y. 

UNITKD STATKS MlIjTARY ACADEMY PRKSS 

1897 







'triwi 



Q« 



J566 



COPYRIGHT, 1897, 
BY 

S. K. TUBMAN. 



i x 






PREFACE. 



This book has been prepared to meet the requirements 
of the very short course in General Chemistry taught to the 
Cadets of the Military Academy. 

The matter embraced is the result of more than sixty 
years' selection and sifting" made in the effort to secure 
that most essential and important for this course. The 
arrangement adopted is that which long experience and 
careful consideration have shown to accomplish the best 
results in the time available for the study of the subject. 

S. E. TILLMAN. 

West Point, N. Y., 
June 15, 1897. 



TABLE OK CONTENTS 



ESSENTIAL PRINCIPLES OF CHEMISTRY. 

PAGES. 

Introductory remarks, Table of Elements 5-7 

Laws of fixed proportions and multiples 8-9 

Atomic theory 9-11 

Chemical notation and nomenclature 11-17 

Chemical reactions and conditions affecting affinity 17-22 

Radicals, bases, acids, and salts m. 22-27 

Equivalent and atomic weights 27-32 

Law of Avogadro and determination of molecular weights 32-35 

Atomic weights from Avogadro's law 35-39 

Number of atoms in molecules, isomorphous relations 39-42 

Volume relations of elements and compounds 42-44 

Relations between specific heats and atomic weights 44-47 

Valency 47-51 

Atomic weights and other properties of elements 51-52 

Stochiometry '. 52-56 

NON-METALS. 

Oxygen and ozone 57-62 

Hydrogen 62-67 

Nitrogen and atmospheric air 07-71 

Water and hydrogen peroxide 71-82 

Carbon and its different forms S3-90 

Compounds of carbon and oxygen 90-97 

Hydrocarbons (methane, acetylene, ethylene) 97-100 

Combustion and flame 100-110 

Silicon and boron 110-113 

Compounds of hydrogen and nitrogen 113-117 

Compounds of nitrogen and oxygen 117-122 

Chlorine and hydrochloric acid 122-125 

Bromine, iodine and fluorine 125-133 

Sulphur 133-136 

Hydrogen sulphide and oxides of sulphur 136-142 

Sulphuric acid, sulphates and other sulphur acids 142-149 

Selenium and tellurium 149-150 



2 

Phosphorus, oxides and oxy-aeids of phosphorus 151-155 

Arsenic and its non-metallic compounds 155-158 

Argon and helium 158 

METALS. 

Potassium and its compounds 159-166 

Sodium and its compounds 166-174 

Ammonium and itscompounds 174-177 

Barium and its compounds 177-178 

Calcium and its compounds 178-184 

Magnesium 184-185 

Zinc and its compounds 186-190 

Aluminum and its compounds 190-195 

Iron, its reduction, metallurgy and important compounds 195-220 

Cobalt, nickel, manganese, chromium 220-222 

Molybdenum, tungsten, uranium, bismuth and antimony 223-224 

Tantalum, niobium and vanadium 224 

Tin and its reduction 224-227 

Titanium, zirconium, thorium, germanium, cerium 227 

Lead, its reduction and important compounds 227-237 

Copper, its reduction and important compounds 237-245 

Silver, its reduction and important compounds 245-252 

Mercury, its reduction and important compounds 252-257 

Platinum and other metals of the same group 257-260 

Gold, its metallurgy and important compounds 260-266 

ORGANIC CHEMISTRY. 

Chemistry of the carbon compounds 267-268 

Classification of carbon compounds 268-270 

Structural and rational formula? 270-271 

Isomerism and polymerism 271 

Saturated hy dr ocarb ons 272 

Unsaturated hydrocarbons 275 

Acetylene series 276 

Benzene series 276 

Terpenes 277 

Camphors, resins, balsams 278 

Caoutchouc, India rubber 279 

Guttapercha 282 

Alcohols 282 

Acetic acid 289 

Acetates... : 291 

Vegetable acids 292 

Ethers 295 

Cyanogen and compounds 296 

Phenols 297 



Carbohydrates 298 

Vegetable colors 305 

Albuminous substances 306 

Alkaloids 308 

APPLICATIONS OF CHEMISTRY. 

Calorific value 311 

Calorific intensity 312 

Glass making 314 

Pottery manufacture 318 

Explosives 322 

Manufacture of coal gas 337 

Alcoholic beverages 343 

Beer making 343 

Wine making 345 

Distilled liquors 348 

Bread making 348 

Fixed oils v 352 

Manufacture of soap 353 

Manufacture of leather 355 

Preparation of cheese 359 



ESSENTIAL PRINCIPLES OF CHEMISTRY. 



The science of chemistry has for its object the study of 
the nature and properties of all kinds of matter and endeav- 
ors to classify the changes which matter undergoes. Nearly 
all substances accessible to man are of a compound nature, 
and may be decomposed or separated into simpler forms of 
matter, these simpler forms being" generally very different 
from the original substances — thus, water is a compound sub- 
stance and may be separated into its constituents which are 
gaseous bodies, oxygen and hydrogen. Common salt is a 
compound, one of its constituents being a white solid and the 
other a yellowish colored gas. 

Those substances which thus far have not been separated 
into simpler forms of matter are called elementary substances 
or simply elements. The terms chemical affinity, chemical 
attraction and force of affinity, have been used to designate that 
force by virtue of which substances enter into combinations 
and form compounds. The compounds which are formed 
under the influence of affinity generally have properties 
entirely different from those of their constituents. 

The force of affinity must be clearly distinguished from 
other forces exerted between all descriptions of matter, such 
as cohesion, which binds together the individual particles of 
the same body, and adhesion which designates the attraction 
existing between the particles of different bodies, as the ad- 
hesion of a liquid to glass; other effects are also observed 
which come under the head of molecular actions. From all 
these, chemical attraction is distinguished by the complete 



change of character which follows its action; it might be 
defined as that property of matter by virtue of which new 
bodies are generated. This property of matter is concerned 
in all chemical changes, and chemistry may be defined as the 
science which investigates the relations ivliicli affinity estab- 
lishes betiveen bodies, determines the laivs governing its action, 
and examines the character and constitution of the substances 
which result from its operation. Chemical changes perma- 
nently affect the properties of bodies, and physical do not. 

There are at present recognized seventy-two elementary 
bodies bnt only sixty-two of this number have been obtained 
in the free state. The existence of the others is established 
from spectroscopic indications and from an examination of 
their compounds. Of the total number fifty-six are usually 
classed as metallic and the others as non-metallic. This divis- 
ion is in part arbitrary since the divisions graduate into each 
other. The accompanying table classifies the elements as 
above stated, the most important being distinguished by 
heavier type and italics. 

These substances present every variety of physical char- 
acter, state of aggregation, etc., some are solid, some liquid 
and some gaseous ; some are light, others heavy, some occur 
in the free state and others only in combination. About six- 
teen elements make up ninety-nine hundredths of all known 
matter. 



Table of Elementary Bodies, with Their Symbols and 
Atomic Weights. 







Metals, 


Isolated. 






NAME. 


SYMBOL. 


ATOMIC 
WEIGHT. 


NAME. 


SYMBOL. 


ATOMIC 
WEIGHT. 


Aluminium, 


Al. 


27.0 


Magnesium, 


Mg. 


24.0 


Antimony,* 


Sb. 


120.0 


Manganese, 


Mn. 


54.0 


Barium, 


Ba. 


137.4 


Mercury, 


Hg. 


200.0 


Bismuth,* 


Bi. 


208.9 


Molybdenum, 


Mo. 


95.5 


Cadmium, 


Cd. 


112.0 


Nickel, 


Ni. 


58.0 


Caesium, 


Cs. 


132.6 


Osmium, 


Os. 


198.5 


Calcium, 


Ca. 


40.0 


Palladium, 


Pd. 


105.7 


Cerium, 


Ce. 


140.4 


Platinum, 


Pt. 


194.4 


Chromium, 


Cr. 


52.0 . 


Potassium, 


K. 


39.1 


Cobalt, 


Co. 


58.9 


Rhodium, 


Rh. 


104.0 


Columbium (orNio- 






Rubidium , 


Rb. 


85.3 


bium ) , 


Cb. 


93.8 


Ruthenium, 


Ru. 


104.2 


Copper, 


Cu. 


63.2 


Silver, 


Ag. 


108.0 


Didymium, 


Di. 


145.4 


Sodium, 


Na. 


23.0 


Gallium, 


Ga. 


70.0 


Strontium, 


Sr. 


87.4 


Glucinum (or Be- 






Thallium , 


Tl. 


203.7 


ryllium ) , 


Gl. 


9.0 


Thorium, 


Th. 


233.4 


Gold, 


Au. 


196.2 


Tin, 


Sn. 


117.7 


Indium, 


In. 


113.4 


Titanium, 


Ti. 


48.0 


Iridium, 


Ir. 


192.7 


Tungsten, 


W. 


183.6 


Iron, 


Fe. 


56.0 


Uranium, 


U. 


239.8 


Lanthanum, 


La. 


138.5 


Vanadium, 


V. 


51.3 


Lead, 


Pb. 


206.9 


Zinc, 


Zn. 


65.0 


Lithium, 


Li. 


7.0 


Zirconium, 


Zr. 


89.4 





Metals, not Isolated. 






Decipium, 


Dp. 


159.0 


Tantalum, f 


Ta. 


182.0 


Erbium, 


E. 


166.0 


Terbium, 


Tr. 


148.8 


Holmium, 


Ho. 


162.0 


Thulium, 


— 


170.4 


Samarium, 


Sm. 


150.0 


Ytterbium, 


Yb. 


89.1 


Scandium, 


Sc. 


44.0 


Yttrium, 


Y. 


172.8 



Non=Metals. 



Argon, 





40.0 


Iodine, 


I. 


126.6 


Arsenic, 


As. 


75.0 


Nitrogen, 


N. 


14.0 


Boron, 


B. 


10.9 


Oxygen, 


O. 


16.0 


Bromine, 


Br. 


79.8 


Phosphorus, 


P. 


31.0 


Carbon, 


C. 


12.0 


Selenium, 


Se. 


78. S 


Chlorine, 


CI. 


35.5 


Silicon, 


Si. 


28.2 


Fluorine, 


F. 


19.0 


Sulphur, 


S. 


32.0 


Hydrogen, 


H. 


1.0 


Tellurium, 


Te. 


128.0 



*Because of their chemical properties Antimony and Bismuth might 
with propriety be classed as non-metals. 

fTlie existence of this body is beyond doubt, but its certain isola- 
tion has not been accomplished, though it is sometimes classed with 
the isolated metals. 



LAW OF FIXED OR DEFINITE PROPORTIONS. 

The relative weights of the constituent elements in any 
chemical compound are fixed— or, the same compound always 
contains the same elements in the same proportions by weight. 
This was the first general law governing chemical action 
discovered; it was recognized before but not fully estab- 
lished until the beginning of this century. Thus in 100 
pounds of water, which is a compound of oxygen and hydro- 
gen, there are always 

88.889 pounds of oxygen 

and 11.111 pounds of hydrogen. 
In 100 grains of lime which is a compound of calcium and 
oxygen there are always 

28.571 grains of oxygen 

and 71.429 grains of calcium. 
The same fixity of proportions exists among the constituents 
of all compounds. 

It is the law of definite proportions which so clearly 
distinguishes true chemical compounds from mere mechan- 
ical mixtures ; in the first the constituents are always in fixed 
proportions, in the mixture they may be in any proportions; 
in a mixture the ingredients may generally be distinguished 
and separated by mechanical means alone, but such means 
are not alone sufficient to distinguish or separate the con- 
stituents of a chemical compound. Again, as has been 
stated, in a chemical compound the properties of the con- 
stituents have entirely disappeared, but in a mixture the 
properties of the ingredients exist in varying degrees 
depending upon the proportions of the ingredients them- 
selves. 

SOLUTIONS AND ALLOYS. 

Although these distinctions characterize true chemical 
compounds and mechanical mixtures there are classes of 
bodies such as solutions and alloys in which these distinc- 
tions do not so plainly exist. Bodies in these states appear 



9 

to be in less intimate condition than trne chemical union and 
more so than that of mechanical mixture. These bodies 
(solutions, alloys, etc.) graduate imperceptibly on the one 
hand into true chemical compounds and on the other into 
mere mixtures. The law governing" the formation of such 
bodies is not known. The word compound in the text is 
always used to indicate a true chemical compound — that is, 
one in which the proportions of the constituents are invar- 
iable and otherwise characterized as above stated. 

LAW OF MULTIPLES. 

The same elements generally unite in more than one pro- 
portion forming different compounds, in such cases the 
proportions of the elements produce simple ratios; the law 
may be more specifically stated as follows: when two todies, 
A and B unite in several proportions the different quantities 
of B which unite ivith a fixed quantity of A bear a simple 
ratio to each other, thus the several quantities of sulphur 
which unite with the same quantity of potassium are to each 
other as the numbers 1, 2, 3, 4 and 5 and the same numbers 
give the different amounts of oxygen which unite with the 
same quantity of nitrogen, as illustrated in the following 
tables : 



POTASSIUM. SULPHUR. 


NITROGEN. 




OXYGEN 


2.438 


1 


1.75 




1. 


2.438 


2 


1.75 




2. 


2.438 


3 


1.75 




3. 


2.438 


4 


1.75 




4. 


2.438 


5 


1.75 




5. 


This is the second 


general law 


governing 


chemical ; 


that was established 


m 









iction 



THE ATOMIC THEORY. 

The above law was discovered by Dalton of Manchester, 
and his writings show that lie had observed it as early as 
1802. From his investigations during 1803 and 1804 he 



10 

gained a clear conception of the law and it is involved in the 
results at which he arrived, though it was not published until 
1805. 

At about the same time, and largely by the consideration 
of the same data that established the Law of Multiples, 
Dalton was led to propose the Atomic Theory, which was 
first published in 1807. This theory, as conceived by Dalton, 
asserts that all simple bodies are composed of small indivis- 
ible particles, or atoms, the atoms of any element having all 
the same weight, which is different from the weight of the 
atoms of all other elements, and chemical compounds result 
from the combination of atoms of different substances. 

The law of definite proportions and the law that the 
quantities of one element which can unite with a constant 
quantity of another increase successively by well defined 
steps and not continuously, or the law of multiples, are both 
reasonably explained by this theory; in the first case it is 
only necessary to conceive that the substance always contains 
the same number of atoms of each of its elements, in the 
second case more than one compound between two elements 
can result only by the successive additions of one or more 
entire atoms. The weight of the particle of the new body 
formed by the union of atoms was by Dalton held to be equal 
to the sum of the weights of the atoms entering it. 

The above is the substance of Dalton' s Atomic Theory. 
In its essential points it has been strengthened by the subse- 
quent test of experimental research and in its expanded form 
is the basis of the developed chemistry of to-day. The 
atoms in Dalton's theory were assumed to be indivisible, but 
the chemistry of to-day merely asserts that they have not 
been divided and not that they cannot be. 

The particles of matter resulting from the combination of 
the same or different kinds of atoms are now termed 
molecules. The same kind of atoms combining form a mole- 
cule of an elementary substance, while different kinds form 



11 

a molecule of a compound substance. The chemical concep- 
tion of molecules is thus clear and defined : 

The molecule is the smallest mass of the substance which 
retains all and only the qualities of the substance itself. 

The body is but an aggregate of molecules, each of which 
has properties identical with those of the body itself If the 
molecule of a compound substance be resolved into its con- 
stituents the properties of the compound are destroyed. 

The atoms ,are the smallest individual masses yet known 
to enter the molecules. They do not ordinarily exist sepa- 
rately, but are combined with the same or different kinds of 
atoms, forming, in the first case, elementary and, in the 
second, compound molecules; compound molecules them- 
selves sometimes unite forming 1 molecules of still greater 
complexity, or molecules of the second order, or even higher 

orders. 

CHEMICAL NOTATION. 

Elements. The atomic theory is expressed in the nota- 
tion employed in chemistry. The symbols of the elements 
are given in the second column of the preceding table. 
The symbols employed are the first letters of the Latin 
names of the elements, a second letter being added when 
the names of more than one element begin with the same 
letter. These symbols represent atoms of their respec- 
tive elements, the different atoms of different substances 
having different weights as already stated. Several atoms 
of the same element are represented by placing a coefficient 
before the symbol or a numeral to the right and below, thus 
three atoms of hydrogen are represented by 

3H or H 3 . 

Compounds. A molecule resulting from the combination 
of atoms of different kinds is represented by placing the 
symbols of the atoms in juxtaposition, thus, a molecule of 
common salt, a compound of sodium and chlorine, is repre- 
sented by NaCl. 



12 

If more than one atom of either element enters the molecule 
it is shown by placing" the corresponding" numeral to the right 
and below the symbol of the element, thus a molecule of 
water is a compound of one atom of oxygen and two of 
hydrogen and is represented by 

OH 2 . 

When it is desired to indicate several molecules the 
numeral is placed as a coefficient or the molecule is enclosed 
in brackets and the numeral placed to the right, thus, three 
molecules of water would be represented by, 

30H 2 or (OH 2 ) 3 . 

A combination of molecules is sometimes indicated by their 
juxtaposition with a comma between, thus the combination 
of zinc oxide (ZnO) and sulphuric oxide (S0 3 ) is indicated 

by 

ZnO,S0 3 ; 

to indicate a group of such molecules they are enclosed in 
brackets and a coefficient placed to the left, thus 

3(ZnO,S0 3 ). 
Combinations of molecules, however, are more generally 
indicated by grouping the symbols of the elements involved 
and placing the proper numerals to the right and below to 
show the number of atoms of each element which enter ; thus 
the compound above would be written 

ZnS0 4 . 

A molecule of water (OH 2 ) combining with a molecule of 
sulphuric oxide (S0 3 ) would form a molecule represented by 

S0 4 H 2 . 

Again, C0 2 combining with OH 2 would give 

C0 3 H 2 . 

These molecules are multiplied by placing a coefficient in 

front as, 

2ZnS0 4 , 3S0 4 H 2 , 5C0 3 H 2 , etc. 



13 
NOMENCLATURE. 

The names of the elements correspond to no fixed rule. 
Some are named in allusion to a certain property, or to a cir- 
cumstance connected with their discovery or history. The 
names of the more recently discovered metals end in um and 
several of the more recent non-metals in ine, as sodium, 
potassium, platinum; chlorine, bromine, etc. 

Binary Compounds. Compounds are termed binary, 
ternary, quaternary, etc., according* as they contain two, 
three or four elements. Binary compounds of metallic 
and non-metallic elements are usually named by changing" 
the termination of the non-metallic element into ide — thus, 
compounds of oxygen, chlorine, sulphur, etc., with metals 
are called respectively oxides, chlorides, sulphides, etc., as 
potassium oxide, sodium chloride, lead sulphide, etc. The 
same method of naming holds in binary compounds of non- 
metallic elements; the termination of the more distinctly 
non-metallic element is changed into ide, thus a combination 
of S and O forms a sulphur oxide, of H and CI a hydrogen 
chloride, of C and O a carbon oxide, etc. 

Oxides. The oxides are very numerous and important and 
for convenience are divided into two principal classes. The 
first class contains all those oxides whose chemical properties 
are similar to those of the oxides of K, Na, Pb, etc., and are 
called basic oxides. The second class contains all those 
oxides whose chemical properties are similar to the oxides of 
S, C, P and N, etc., and are called acid oxides; generally the 
oxides of the metals are basic and of the non-metals acid. 
Some of the acid and basic oxides are capable of uniting 
directly and forming compounds called salts, thus when the 
oxide of sulphur (S0 3 ) in vapor, is passed over heated 
barium oxide (BaO), combination ensues and a salt called 
barium sulphate (BaS0 4 ) is formed. There is also an inter- 
mediate group of oxides designated as neutral oxides because 



14 

of their slight disposition to enter into combination; man- 
ganese dioxide (Mn0 2 ) is an example of this class. These 
neutral oxides may also be formed from non-metals ; water 
(H 2 0) and carbon monoxide (CO) are examples. These 
classes are not separated by distinct lines but graduate into 
each other; the same oxide may sometimes exhibit either 
acid or basic properties according to circumstances. Again, 
although the most characteristic basic oxides are oxides of 
the metals, yet some of the higher metallic oxides exhibit 
acid properties and some of the metals form only acid oxides. 

Oxy- Acids. Most of the acid oxides unite readily with 
water forming compounds called oxy-acids, which possess to 
a marked degree the properties termed acid, such as sour 
taste, corrosive action, the power of reddening certain blue 
vegetable colors and yet more important, the power of 
exchanging the hydrogen which they contain for a metal and 
forming salts. Thus the oxide of sulphur (S0 3 ) called 
sulphuric oxide, unites energetically with water (OH 2 ) form- 
ing sulphuric acid, the formula for which is SOJI 2 . Again 
the oxide of nitrogen (N2O5), called nitrogen pentoxide, will 
unite with water forming nitric acid (N 2 6 H 2 ) or 2N0 3 H. 
Carbon dioxide (C0 2 ) also unites with water forming (C0 3 
H 2 ) carbonic acid. Sulphuric or nitric acid will act upon zinc 
and exchange its hydrogen for the metal and form a salt 
called zinc sulphate or zinc nitrate. The property of 
exchanging their hydrogen for a metal is the most character- 
istic property of acids and will be referred to again. It is 
now seen that salts may be formed in two ways, either by the 
direct union of basic and acid oxides or by the replacement 
of the hydrogen in an acid by a metal. 

Prefixes. Binary compounds of oxygen following the 
law of multiples are distinguished as mono, di, tri, etc., ac- 
cording to the degree of oxidation, a compound intermediate 
between a monoxide and a dioxide is called a sesquioxide, as 



15 

CrO, chromium monoxide; 

Cr0 2 , chromium dioxide; 

CrOs, chromium trioxide; 

Cr 2 3 , chromium sesquioxide; etc. 

Binary compounds of the other elements under the same 
law are designated in the same way, as, 

monosulphide, monochloride, 

disulphide, dichloride, 

etc. etc. 

Suffixes. When an element forms but two oxides they 
are also often distinguished by placing before the word oxide 
the name of the element with the termination ous for the 
lower, and ic for the higher oxide, thus 

Sulphurous oxide, S0 2 . 
Sulphuric oxide, S0 3 . 
Carbon dioxide, C0 2 . 

These same terminations are also used to specify the two 
more important oxides of an element even when it forms 
more than two oxides, thus, the basic salifiable (salt forming) 
oxides of iron are 

FeO, ferrous oxide, 

Fe 2 3 , ferric oxide. 

The salts which are formed from such oxides have the same 
terminations, as ferrous and ferric salts. 

It has been stated that the acid oxides unite with water, 
forming oxy-acids, and that these acids may form compounds 
called salts, by exchanging their hydrogen for a metal. If 
the name of the oxide terminates in ous the name of the acid 
formed by its union with water also terminates in ous, thus 

Sulphurous oxide unites with water and forms sulphurous 
acid; 

Nitrous oxide unites with water and forms nitrous acid; 

Phosphorous oxide unites with water and forms phos- 
phorous acid. 



16 

The salts which result from these acids by exchanging 
their hydrogen for a metal, have the termination ite — thus, 
salts from sulphurous acid are called sulphites, from nitrous 
acid, nitrites; as, lead sulphite, potassium nitrite, etc. If 
the oxide terminates in ic the acid formed by its union with 
water has the same termination — thus 

Sulphuric oxide unites with water, forming sulphuric acid; 
Nitric oxide unites with water, forming nitric acid; 
Phosphoric oxide unites with water, forming phosphoric 

acid; 
Carbon dioxide unites with water, forming carbonic acid, 

etc., etc. 

The salts which result from the oxy-acids ending in ic, by 
an exchange of hydrogen for a metal, have the termination 
ate, thus salts from the last named acids are sulphates, 
nitrates, phosphates, respectively — as lead sulphate, potas- 
sium nitrate, etc. 

In naming binary compounds, the Latin prefixes uni, bi, 
ter, etc., are sometimes used instead of the Greek, but the 
latter are more generally employed. 

Hydr acids. The acids above referred to are all oxy-acids 
and it was once supposed that all acids contained oxygen. 
We now know that there are bodies possessing all the 
properties of acids which do not contain oxygen, they all, 
however, contain hydrogen and they are capable of exchang- 
ing this hydrogen for a metal and forming salts. Some of 
the acids which contain no oxygen are composed of hydro- 
gen and one other element. There are only a few such 
examples, some of them are — hydrochloric acid (HG1), 
hydrobromic acid (HBr), hydrofluoric acid (HF), sulphydric 
acid (SH 2 ). The salts formed by replacing the hydrogen in 
the hydracids by a metal are named in accordance with the 
rule for binary compounds. Thus, when the hydrogen in 
hydrochloric acid is replaced by zinc, we have zinc chloride 



17 

— if potassium replace the hydrogen, in hydrobromic acid, we 
have potassium bromide, etc. 

The above system of nomenclature is the one most 
generally followed, but there are slight departures from it 
by certain chemists. The principle of the system is that the 
composition . of the compound shall be briefly expressed in 
its name. In addition to this, many substances have popular 
names which will be found in the text, or have been other- 
wise named as will be subsequently explained. 

CHEMICAL REACTIONS. 

Nearly all chemical changes result from the reciprocal 
action of chemical agents upon each other and are therefore 
called reactions. Those substances which differ most in 
chemical properties act most readily upon each other. From 
the definition of molecules it is evident that these changes 
take place among the molecules, and although these mole- 
cules are invisible it should be appreciated that whatever 
chemical changes occur in the bodies must come through an 
alteration of their molecules. By means of the symbols 
given we can represent the changes which occur. Reactions 
are usually represented by equations, in the first member of 
which are placed the symbols of the substances employed 
called reagents, and in the second member the symbols of the 
products obtained. Reactions consist either in the direct 
addition or separation of elements, or in the substitution of 
an atom of one element for one or more atoms of another 
element, or of a group of atoms of one molecule for a similar 
group of another. 

We thus have first, synthetical reactions in which a more 
complex body is formed by the union of simpler bodies; in 
this case the bodies should be opposed in properties. 
Thus— 

BaO+S03=BaS0 4 Pb+0=PbO. 

2 



18 

Second, analytical reactions, as when calcium carbonate 
is heated it yields calcinm oxide and carbon dioxide, thus — 

CaC0 3 heated=CaO+C0 2 . 

In this class a more complex body is broken into simpler 
ones. 

Third, metathetical reactions, in which the transforma- 
tion of previously existing compounds is brought about 
either by simple substitution or double decomposition, thus — 

Zn+2HCl=ZnCl 2 +H 2 

NaCl+AgN0 3 =AgCl+NaN0 3 . 

In the case of double decomposition, if the body desired be a 
salt, one of the reagents must contain the acid part and the 
other the basic part of the salt desired. 

These equations are but the expressions of observed 
facts, and their truth is known from observation, and not 
from deduction. They express only the known results from 
known premises and give no indication of the complex 
phenomenon of the reaction itself. They represent the 
distribution of weights before and after chemical change. 
In every reaction, since there is only a change, and not a 
loss or destruction of matter, the total weights of matter in 
the two members must be the same, as also must be the total 
number of atoms of each and all the elements. Some 
substances occur native, but the majority of them are 
obtained by one or the other of the above methods. The 
most common reactions are of the metathetical kind. 

Affinity has been defined as a property of matter by 
which new compounds are formed. It is frequently con- 
ceived to be the cause of chemical action and hence termed 
the force of affinity. It is essentially concerned with action 
between atoms but also extends to action between molecules. 
Without limiting the conception of affinity it is convenient 
to adhere to the practice of designating it as a force. There 
are conditions and circumstances under which reactions 



19 

occur more readily than others and the force of affinity may 
be said to vary with conditions, and except under entirely 
known conditions it is entirely impossible to predict the 
result of an experiment. As illustrating- the above state- 
ments we may refer to certain adventitious circumstances 
which influence chemical actions or their results. 

CONDITIONS AFFECTING AFFINITY. 

Insolubility. It is a rule almost without exception that 
when two soluble salts, containing the constituents of an 
insoluble, or sparingly soluble one, are brought together in 
solution the salts decompose each other and the less soluble 
salt is formed. This rule may be illustrated by bringing 
together in solution ammonium carbonate and calcium 
chloride, when the calcium carbonate will be formed and 
precipitated, as indicated by the reaction: 

(NH,) 2 C0 3 +CaCl 2 =CaC03+2NH 4 Cl. 

Volatility. In many instances when hvo salts, containing 
the constituents of a volatile one, are heated together the 
volatile one is produced and driven off. This is illustrated 
when calcium carbonate and ammonium chloride are heated 
together, ammonium carbonate is formed and volatilized. 

CaC03+2NH 4 Cl (heated) =CaCl 2 +(NH 4 ) 2 C0 3 . 

Again, certain acids or acid oxides which are volatile 
may be displaced by others of feebler attraction, but which 
are not volatile. 

Solution. The force of affinity acts only at insensible 
distances and whatever tends to prevent the closest prox- 
imity of the molecules tends to prevent action. Owing to 
cohesion in solids and the distance between the particles in 
the gaseous state, neither of these is most favorable to 
chemical action. In solution cohesion is slight, and the 
distance between particles is small, and this is the mosl 
favorable state for chemical action, consequently it is often 



20 

desirable to bring one or both of the bodies to a state of 
solution. 

Of the other causes which affect the force of affinity we 
may mention Temperature, for at one temperature mercury 
unites with oxygen, and at a different temperature the 
oxygen separates from it. 

Physical Surroundings. If the vapor of water be passed 
over heated iron filings it is decomposed and iron oxide is 
formed; on the other hand, if hydrogen gas be passed over 
heated iron oxide it reduces it to the metallic state, while the 
vapor of water is reformed. 

3Fe+40H 2 =Fe 3 4 +H>. 
H 8 +Fe 3 4 =3Fe+40H 2 . 

Again, if sulphydric acid gas in excess be passed over 
acid potassium carbonate, slightly heated, carbon dioxide is 
liberated and potassium sulphide formed, whereas, if carbon 
dioxide be passed through a solution of potassium sulphide 
the acid carbonate is reformed and sulphydric acid gas 
passes off. 

The nascent state is one very favorable to chemical 
action ; this is the condition in which bodies exist when just 
liberated from some combination. Thus, if free hydrogen be 
passed into nitric acid there is no action, but if the acid act 
upon zinc immersed in it the hydrogen set free decomposes 
a portion of the acid. 

Catalytic Action. This refers to effects which are ap- 
parently brought about by the mere presence of a body. 
Thus, if potassium chlorate be heated with manganese 
dioxide it is decomposed more easily than when heated 
alone. The same effect is produced by the presence of other 
oxides, and is probably due to the fact that these oxides pass 
to a state of higher oxidation and then in turn are themselves 
reduced. Only oxides capable of higher oxidation produce 
the result. 



21 

Disposing Affinity. This term is used to embrace an 
extensive class of actions which are induced by the presence 
of certain bodies and which would not occur in their absence. 
It differs from the catalytic action in that the disposing body 
is found to be changed at the close of the operation, while 
the influencing body in catalysis is not. 

It should be understood that these so-called cases of 
modified chemical action are only the statements of facts 
invariably observed. These facts will soon undoubtedly be 
included under the more perfectly developed laws govern- 
ing chemical action. Many examples of this action will be 
observed as progress is made in the course. 

Influence of Pressure on Chemical Action. When a 
body is decomposed, in a confined space, by heat, some 
of the products being gaseous, the decomposition will go on 
until the liberated gas or vapor has attained a certain pres- 
sure, greater or less according to the temperature. No 
further decomposition will then take place nor will the 
elements or constituent gases recombine so long as the tem- 
perature remains fixed; but if the temperature be raised the 
decomposition will begin again and continue until the vapor 
reaches a tension definite for that temperature, when it will 
again cease; if on the other hand, the temperature is lowered, 
recombination ensues until the tension of the remaining 
gases is reduced to that corresponding to the lower temper- 
ature. Decomposition under these conditions has been 
designated by Deville by the term " Dissociation." 

The effect of pressure is also seen in the retarding - influence it exerts 
in the action of acids upon zinc. If the escape of the gas which is lib- 
erated is prevented the action is retarded. On the other hand, there 
are numerous reactions which are greatly promoted by increased 
pressure, such as those which depend on the solution of gases in Liquids, 
or on the prolonged contact of substances which under ordinary cir- 
cumstances would be volatilized by heat. 



22 

RADICALS, BASES, ACIDS, AND SALTS. 

We are now prepared to supplement the system of nom- 
enclature given, to a certain extent, and to explain the use of 
certain terms which have long been, and still are in nse in 
chemistry, and to more fully define others which we have 
already used. 

Radicals. In the metathetical reactions it was indicated 
that the elementary atoms not only change places with each 
other, atom for atom, but one atom with more than one of 
another kind, or one with a group of other kinds or groups 
of atoms of different kinds with each other. These inter- 
changing atoms or groups appear to bear the same relations 
to the molecules they enter as did the atom or atoms replaced. 
Thus, in the following reactions — 

AgN0 3 +NaCl=AgCl-hNaN0 3 , 
AgN0 3 +NH 4 Cl=NH 4 N03+AgCl, 

the atom of silver is replaced in the first by an atom of 
sodium, in the second by the group (NH 4 ). Such groups of 
atoms are called compound radicals, and it is assumed that in 
ordinary reactions they are transferred from molecule to 
molecule without loss of integrity. The elementary atoms 
which perform similar parts in different molecules may be 
called elementary radicals, so that the term radical is appli- 
cable to both elementary atoms and groups of atoms. Only 
a few of the compound radicals have been isolated. They 
are assumed to so exist because the same group, or, at least 
the same proportional amounts of the same elements enter 
several compounds. The symbol of every compound mole- 
cule may be formulated into possible radicals, but unless the 
radicals enter several compounds there is nothing gained by 
the assumption. Radicals are designated as acid or basic 
according as they fulfill the parts of acid or basic compounds. 
Of elementary radicals, generally the metallic atoms are 
basic, and the non-metallic atoms acid radicals. Thus, in 



23 

NaCl the sodium is the basic and the chlorine the acid radi- 
cal. In ternary combinations the compounds of oxygen with 
the metals are usually basic radicals and the compounds of 
oxygen with the non-metals acid radicals. Thus, in 3K 2 0, 
As 2 5 , the molecule K 2 is basic, the other the acid radical; 
in Na 2 S0 4 the Na 2 is the basic, and the S0 4 the acid radical. 
Compound radicals consisting" of carbon and hydrogen only, 
are usually basic, but those which contain oxygen also, are 
generally acid. The radical NH 4 is strongly basic. The 
basic radicals are also called electro-positive, and the acid 
electro-negative radicals. 

Bases. This term is more general than basic oxide 
(already-mentioned) and includes a class of bodies desig- 
nated basic hydrates, simply hydrates or better hydroxides 
These hydrates were formerly supposed to contain water as 
such, but now they are believed to contain oxygen and hydro- 
gen in the form of hydroxyl (OH) and not in the form of 
water (OH 2 ). They can usually be formed from water by 
replacing half its hydrogen by a metallic element. Thus, 

20H 2 +K 2 =2KOH+H 2 
20H 2 +Na 2 =2NaOH+H 2 . 

These hydroxides of potassium and sodium and also those of 
lithium, caesium and rubidium are very soluble in water and 
give solutions which corrode the skin and convert fats into 
soaps ; they differ from the hydroxides of all other metals 
(except that of barium) in that they are not decomposable 
by heat alone. Very similar to them in chemical properties 
is the hydroxide of ammonium formed by dissolving ammonia 
gas (NH 3 ) in water. All of the hydroxides just named are 
called alkalies. The great similarity of ammonium hydroxide 
to the others named gives grounds for the assumption that 

the radical NH 4 

exists, and that amnionic hydroxide may be formulated, X 11 ,0 1 1 
just as potassic hydroxide is : K01J . 



24 

The hydroxides of Ba, Ca, Sr and Mg are called alkaline 
earths. They are less soluble than the alkalies, less caustic, 
and, except that of Ba, can be decomposed by heat into a 
metallic oxide and water. Thus, 

Ca0 2 H 2 +heat=CaO+OH 2 . 

This process may be reversed, and the hydroxide obtained by 
mixing the metallic oxide with water. Thus, 

CaO+OH 2 =Ca0 2 H 2 = Calcic hydroxide. 

The hydroxides of this group can also be obtained by replac- 
ing half the hydrogen in water by the metallic atom, thus — 

Ca+20H 2 =Ca0 2 H 2 +H 2 , . 
Ba+20H 2 =Ba0 2 H 2 +H 2 . 

The hydroxides of many of the other metals are still more readily 
decomposed by heat, and can not as a rule be formed direct from the 
(jxides and water. They may be obtained by adding a solution of a 
soluble salt of the metal to one of the hydrates named above. Thus, 

ZnCl 2 +2KOH=2KCl+ZnO,H,>. 
The hydroxides may all be regarded as compounded of metallic atoms 
with the radical hydroxy! (OH). Thus, 

KOH. 

Ca(OH),. 

0r 2 (OH) 6 . 

Metallic Oxides, Basic Anhydrides. Just as hydroxides 
are obtained by replacing half the hydrogen in water by a 
metallic atom or basic radical, so the metallic oxides or basic 
anhydrides may be considered as formed by a replacement 
of all the hydrogen in one or more molecules of water by 
metallic atoms. Thus, 

K 2 +OH 2 =K 2 0+H 2 . Ca+OH 2 =CaO+H 2 . 

The term base in inorganic chemistry is generally applied 
to both hydrates and basic anhydrides and also to certain 
compound radicals, all of which form salts with acids, but 
there is a tendency to limit the term to hydroxides. 

Acids. The general properties of acids have already been 
stated, the most characteristic of which is their capacity to 



25 

exchange a part or the whole of the hydrogen which they 
contain for metallic elements or basic radicals. Some of the 
acids contain only hydrogen and one other element, as 
hydrochloric acid (HC1), hydrobromic acid (HBr), sulphy- 
dric acid (SH 2 ), &c, but most acids consist of hydrogen 
and more than one other element, as H 2 S0 4 , sulphuric acid; 
HN0 3 , nitric acid; C0 3 H 2 , carbonic acid; &c. 

The hydrogen in all these acids may be replaced in 
several ways — by acting on the acid with either a metal, 
metallic oxide, hydroxide or a metallic salt. Thus, 

H 2 S0 4 +Na 2 =Na 2 S0 4 +H 2 . 

2HCl+ZnO=ZnCl 2 +OH 2 . 

HBr+KOH=KBr+OH 2 . 

Ca0 2 H 2 +S0 4 H 2 =S0 4 Ca+20H 2 

NH 4 OH+N0 3 H=NH 4 N0 3 +OH 2 

HCl+AgN0 3 =AgCl+HN0 3 . 
It is thus seen that although salts are sometimes formed by 
the direct union of a basic and an acid oxide (see page 13) 
they are far more generally formed by the replacement 
of the hydrogen in an acid, in part or whole, by a basic 
radical either elementary or compound. 

The acids without oxygen are called hydrogen acids, or 
hydracids, and those containing it oxygen acids or oxy -acids. 
The oxygen acids like the hydrates may be regarded as 
compounds of hydroxyl with an acid radical instead of with 
a basic radical. Thus, 

Nitric acid, N0 3 H=N0 2 (OH) ; 
Sulphuric acid, S0 4 H 2 =S0 2 (OH) 2 . 

Basicity of Acids. When an acid contains but one atom 
of hydrogen in its molecule replaceable by a metal or basic 
radical it is said to be monobasic; when two, bibasic; when 
three, tribasic; &c. 

Monobasic acids can form but one class of salts, the metal 
replacing the whole of the hydrogen in one or more mole- 
cules of the acid. Thus, 



26 

HC1+K=KC1+H, 
2HCl+Zn=ZnCl a +H 2 . 

A bibasic acid may form two classes of salts, viz.: — 
primary or acid salts in which only half the hydrogen in the 
molecule is replaced, and secondary salts in which the whole 
is replaced; in the latter case if the hydrogen is replaced by 
one metal the salt is called normal, and if by two metals 
double. Tims, 

KHSO4 is an acid salt, acid potassium sulphate. 

K2SO4 is a normal salt, normal * 

KNaS0 4 is a double salt, potassio-sodic 

Tribasic acio^s may form three classes of salts — primary, 
secondary or tertiary, including' normal, double and triple, in 
which the hydrogen is wholly or partially replaced by one or 
more metals. The following list contains the most important 
and common inorganic acids, arranged according to basicity: 



MONOBASIC 


ACIDS. 


BIBASIC ACIDS 


TRIBASIC ACIDS. 


Hydrochloric, 


HC1. 


Hydric (water) OH 2 . 


Orthophosphoric 


Hydrobromic, 


HBr. 


Sulphydric, SH 2 . 


H 3 PQ 4 


Hydriodic, 


HI. 


Sulphuric, S0 4 H 2 . 




Hydrofluoric, 


HF. 


Carbonic, C0 3 H 2 . 




Nitrous, 


HN0 2 . 


Pyrosulphuric, H 2 S 2 7 . 




Nitric, 


HNO3. 






Chloric, 


HCIO3. 







Acid Anhydrides. The application of the term acid oxide has been 
already given (page 13). Many of these oxides can be obtained by 
abstracting the constituents of water from acids, and hence have also 
received the names of acid anhydrides or simply, anhydrides. 

As has been stated, most of these anhydrides display great readi- 
ness to unite with water, forming acids. Thus, 

S0 3 +H 2 0=H 2 S0 4 . 
In this respect they bear the same relation to acids that basic oxides do 
to hydrates. 

Salts. The formation of salts by the direct nnion of acid 
and basic oxides, and by the replacement of the hydrogen in 
an acid, by different methods, have been already referred to. 
Now it is evident that, in the reaction between acids and 
hydroxides, while we considered that the hydrogen of the acid 



27 

was replaced by a metallic atom or basic radical, we might, 
with equal propriety, have considered the hydrogen of the 
hydrate as replaced by an acid radical, thns : 
KOH+N0 2 OH=KNO,+H 2 0. 
From these considerations it is evident that the term salt is 
'a descriptive one and cannot be defined in independent lan- 
guage. 

If only a part of the hydrogen in the hydroxide be replaced 
by the acid radical the salt is called basic. Basic salts are 
also defined as those formed by the union of a normal salt 
with a basic oxide or hydroxide, the base thus being in excess 
of that necessary to form a normal salt. On the other hand, 
a normal salt may combine with an acid oxide so that there 
is an excess of acid oxide over that necessary to form a 
normal salt: such a salt is called an anhydro salt. 

EQUIVALENT WEIGHTS OR EQUIVALENTS. 

It has already been stated that substances may replace each 
other in combination and that chemical actions generally 
consist of an interchange between the elements of different 
molecules. When HC1 acts upon Zn, the zinc replaces the 
hydrogen, which is envolved as a gas; when potassium is 
thrown upon water it replaces the hydrogen of the water 
forming KOH; if mercury be added to a solution of silver 
nitrate the silver is replaced by the mercury and itself 
deposited. 

The replacement of one element by another always takes 
place in fixed proportions. The relative quantities of the 
elements which thus replace each other in combination ((re 
called equivalent iveights or chemical equivalents. Equivalent 
weights are those quantities of the elements which possess 
the same chemical value and are capable of filling each 
other's places directly or indirectly. The chemical equivalent^ 
are made specific by defining thou as those weights which will 
combine with or displace, or ((re chemically equivalent to. one 
part by weight of hydrogen. 



28 

Strictly speaking, quantities of elements could only be 
said to be equivalent when they had actually replaced each 
other in combination, but quantities of elements which are 
equivalent to the same quantity of another element are 
assumed to be equivalent to each other, thus 35.5 parts of 
chlorine are known to unite with 1 part of hydrogen, 23 of 
sodium and 108 of silver, consequently the numbers 1, 23 and 
108 are the equivalent weights of hydrogen, sodium and sil- 
ver. In a similar way the equivalents of all elements may 
be expressed. 

These equivalents are the result of direct experiment and 
are based on no hypothesis as regards the constitution of 
matter. But in addition to the fact that many of the equiv- 
alent weights have to be determined indirectly there is 
another difficulty which arises as soon as we consider those 
bodies which combine in more than one proportion, thus, tin 
forms two chlorides in one of which 58.5 parts of the metal 
are combined with 35.5 parts of chlorine and in the other 
29.25 parts of tin are combined with the same amount of 
chlorine; which of these is to be taken as the equivalent 
weight of tin? The same difficulty is encountered in all 
cases in which combination occurs in more than one propor- 
tion between elements, and as most bodies combine in more 
than one proportion the idea of equivalent weights is not 
definite. 

ATOMIC WEIGHTS. 

The distinction between atoms and molecules has already 
been given and although 'the atom is the smallest mass 
of matter yet distinguished, the modern chemistry does not 
assert that the atom is beyond the limit of divisibility, it 
simply asserts that it has not yet been divided and that in all 
Jmown chemical processes the atomic masses act as units, 
and it matters not what may yet be accomplished in dividing 
atoms, their integrity is retained in all reactions with which 
we are at present familiar. 



29 

With the promulgation of the atomic theory the deter- 
mination of the relative weights of the elementary masses or 
the relative combining" numbers became an absorbing 
problem. These weights are the numerical constants of 
the science of Chemistry — they are the essential data in all 
quantitative analysis as well as in the application of 
Chemistry to the necessities of daily life. To make possible 
a clear understanding of the method of determining atomic 
weights the student must bear in mind that although we 
cannot isolate and operate upon a single molecule of a body, 
yet in transforming a body we but transform its individual 
molecules and whatever change the body undergoes is also 
undergone by each molecule thereof and whatever relation is 
found to exist among the constituents of a body also exists 
among the constituents of a single molecule. 

Determination of Atomic Weights by Analysis. By ac- 
curate analysis we can determine the proportions of the 
elements which enter many compounds and consequently the 
proportions of the elements which enter the molecules, and 
if we knew the number of atoms of each element in the 
molecule we could deduce the relative weights of the atoms. 

Thus, the analysis of water shows that oxygen and 
hydrogen enter the molecule in the proportion by weight of 
oxygen =8 and hydrogen =1. If there were an equal number 
of atoms of each element in the molecule the numbers 8 and 
1 would represent the atomic weights. Now there is another 
compound of oxygen and hydrogen in which the proportions 
by weight are oxygen = 16 and hydrogen =1. Assuming from 
the first compound that the atomic weights are 8 and 1 we 
might in the second case conclude that the compound 
contained two atoms of oxygen; this would then account for 
the new proportion 1(> to 1, but if we, with equal propriety, 
assume that the second compound contains one atom of each 
of the elements then the relative atomic weights are 1(> and 1 
and the first compound, water, necessarily contains two 
atoms of hydrogen. 



30 

Thus with nothing before ns except the results of simple 
analysis, the atomic weights would be uncertain, they might 
be correct or they might be multiples or sub-multiples of the 
correct ones, depending upon whether or not the number of 
atoms which enter the molecule was correctly assumed. 

Determination of Atomic Weights by Substitution. The 

method of substituting one element for another can often be 
made use of to assist in reaching a correct conclusion as to 
the number of atoms which enter the molecule. 

For example, if water be treated with metallic sodium it 
is acted upon in such a way as to produce a substance whose 
composition is 

Sodium, Hydrogen, Oxygen 
23 1 16 

and if this compound be evaporated to dryness and heated 
with more sodium the remaining portion of the hydrogen is 
driven out and replaced by the sodium and we have a com- 
pound of 

Sodium, Sodium and Oxygen. 
23 23 16 

It is thus evident that the hydrogen in the molecule of water 
has been replaced by halves and it follows from the concep- 
tion of atoms that there must have been at least two atoms 
in the molecule. Now if we could be certain that the 
molecule contained only one atom of oxygen we would again 
have the atomic weights of hydrogen and oxygen to be 1 and 
16. With only the data yet before us we could not certainly 
conclude that the molecule of water has but one atom of 
oxygen and hence the atomic weights would still be un- 
certain. 

Again, if we take marsh gas, a compound of carbon and 
hydrogen, the hydrogen may be replaced by four separate 
substitutions, so that there must be at least four atoms of 
hydrogen in the molecule of marsh gas and if it be assumed 



31 

that they are combined with one atom of carbon we arrive 
directly at the atomic weights. But as in the preceding case 1 
the number of atoms of each element is not determined by 
substitution alone and the atomic weights would remain 
uncertain. 

Determination of Atomic Weights by Decomposition. By 

the decomposition of certain bodies and the formation of 
others it is sometimes possible to compare the amounts of a 
certain element in the two and if the number of atoms of the 
element in either be known the number in the other is also 
determined. 

The above are the only purely chemical means for the deter- 
mination of atomic weights and it is seen that they leave a 
doubt as to the correct numbers. It should be borne in mind 
that by a combination of all the methods and by an examin- 
ation and comparison of various compounds of the same 
element the uncertainty is very small. Thus, in the case of 
carbon it is indisputable that the smallest increment or decre- 
ment which can be made in any compound is 12 times as 
great as the smallest weight of hydrogen that can be intro- 
duced or displaced and if we adhere to the smallest separable 
portion as the atom, the uncertainty as to the atomic weight 
is exceedingly slight in the case of this and many other 
elements. 

These purely chemical methods for the determination of 
atomic weights have been supplemented by means dependent 
upon physical considerations. The coincidences between the 
results obtained by these different means are so satisfactory 
as to dispel doubt as to the correct atomic weights of the 
great maiority of the elements except such doubt as is due to 
imperfection of process. We will now explain the method of 
determining the atomic weight by the introduction of physi- 
cal considerations. 



32 

PHYSICAL AND CHEMICAL RELATION OF ATOMIC 
WEIGHTS. 

Law of Ayogadro. From a consideration of the relations 
existing between the specific gravities and the determined 
atomic weights of certain elements, Avogadro, an Italian, in 
1811 was led to propose the hypothesis that equal volumes of 
all gases under like conditions of temperature and pressure con- 
tain the same number of molecules. 

The hypothesis uses the word molecule in the sense already 
given and involves the idea that the elements in their inter- 
nal structures are analogous to compounds and that the 
molecules of elementary bodies may contain more than one 
atom, and it will later appear that there are good reasons for 
such belief. This hypothesis has become of fundamental 
importance in chemistry in determining- molecular weights 
and settling atomic weights ; it is supported by the results of 
all investigations made to determine the internal structure of 
gases, and upon the theory of molecular mechanics it affords 
a mathematical explanation of the laws of compression and 
temperature, and if the mechanical theory of gases be 
accepted the hypothesis of Avogadro follows as a mathe- 
matical necessity; from these considerations the hypothesis is 
to-day justly considered a law. 

Accepting the hypothesis as a physical law an important 
corollary follows directly — viz.: The molecular weights of 
substances are directly proportional to their specific gravities 
in the gaseous state, or the actual weights of the molecules of 
substances are to each other as the actual weights of equal vol- 
umes of the substances in the gaseous state, under like 'condi- 
tions of temperature and pressure. 

Determination of Molecular Weights. It is therefore plain 
that the weights of the molecules of different gases may be 
readily obtained in terms of the weight of the molecule of 
any gas assumed as a standard by simply determining their 
specific gravities, with reference to the standard gas. It 



33 

simplifies the comprehension of the subject here considered 
to adopt hydrogen as the standard for specific gravities. 

To illustrate the above method, let us suppose that a vol- 
ume of oxygen weighs sixteen times as much as an equal 
volume of hydrogen, then since these volumes contain the 
same number of molecules the molecule of oxygen will weigh 
sixteen times as much as the molecule of hydrogen; or if a 
given volume of hydrochloric acid weigh 18.25 times as much 
as an equal volume of hydrogen the molecule of HC1 will 
weigh 18.25 times as much as the molecule of H. 

Now if we also take the weight of the hydrogen molecule 
as the standard for molecular weights the molecular weights 
and specific gravities will be represented by the same num- 
bers, thus, the specific gravity of oxygen referred to 
hydrogen is 16, the molecule of oxygen weighs 16 times as 
much as the molecule of hydrogen and if the weight of the 
hydrogen molecule be taken as unity the weight of the oxygen 
molecule is 16; therefore when hydrogen is used as the 
standard for specific gravities and the weight of the hydrogen 
molecule as the standard for molecular weights the molecular 
weights and specific gravities are indicated by the same 
numbers. 

Now if we should use half the weight of the hydrogen 
molecule as the standard for molecular weights it is evident 
that the molecular weights would all be double what they 
were when we used the whole molecule as the standard and 
then instead of being indicated by the same numbers as 
specific gravities the molecular weights would be the doubles 
of the specific gravities. For reasons which will appear 
subsequently it is found convenient to use the weight of half 
of the hydrogen molecule as the standard for molecular 
weights. 

For convenience, we shall, following Prof. Cooke, call the 
weight of the half hydrogen molecule a microcrith and in 
writing it shall abbreviate it to m. c. Now bearing in mind 
3 



34 

that the molecular weights of substances are the actual 
weights of their molecules in terms of some standard, we 
may say that the molecular weights of all gases may be 
obtained in m. c. by doubling their specific gravities referred 
to hydrogen as the standard; e.g., the specific gravity of 
HC1 is 18.25 the weight of its molecule in m. c. is therefore 
36.5 — the specific gravity of XH 3 is 8.5 and the weight of its 
molecule is 17 m. c. 

In most cases by chemical analysis we can determine 
accurately the proportions of the constituents which obtain 
in any compound, thus, in the case of water, analysis shows 
that it is composed of one part by weight of hydrogen to 
eight of oxygen, but this proportion of 1 to 8 holds also with 
the numbers 2 and 16, 3 and 24, 4 and 32, &x?., and from the 
proportion alone we cannot tell which of the numbers (9, 18, 
27, 36, &c.,) is the molecular weight of water vapor, but by 
finding the specific gravity of water vapor (which is 9) and 
doubling it, we are enabled to decide that 18 is the molecular 
weight— that is, a molecule of water vapor weighs 18 m. c. 

It should be observed that the determination of the specific 
gravity of a compound gas is a less accurate operation than 
the analysis of the gas. The analysis gives an accurate num- 
ber (the combining number of the gas or gases under 
consideration) and the specific gravity merely tells what 
multiple of that number to take. 

Thus from the law of Avogadro we are enabled very 
simply to decide whether a number is the molecular weight 
or a multiple or sub-multiple of it. This method of deter- 
mining molecular weights is clearly only applicable to 
volatile substances, the molecular weights of the non-volatile 
substances must be determined in other ways. 

OTHER METHODS OF DETERMINING MOLECULAR WEIGHTS. 

The determination of the molecular weights of substances from 
their gaseous specific gravities is the most important but not the only 
method of determining molecular weights. Several other methods 
have become available but thev can onlv be here mentioned. 



35 

Molecular Weights from Osmotic Pressure. The mixing of dis- 
similar substances, gases, liquids or solids in solution, through 
membranous diaphragms is in general termed osmose. Membranous 
bodies, such as rubber, parchment, &c, permit the passage of molecules 
of different substances with very unequal facility. If a solution of a 
substance be separated from a quantity of the pure solvent by a 
proper diaphragm or osmotic membrane, a certain pressure will be 
exerted on the membrane from the side of the dissolved substance. 
This pressure is called osmotic pressure. 

It has been found that the osmotic pressure is directly proportional 
to the weight of the dissolved substance in a unit of volume of the 
solvent and this pressure varies directly as the absolute temperature of 
the solution. From these and other considerations it seems highly 
probable that equal volumes of different solutions at the same tem- 
perature and osmotic pressure contain the same number of molecules 
of the dissolved substances. From this conclusion it is possible to 
determine molecular weights. A solution of a solid whose molecular 
weight is unknown may be prepared so that its osmotic pressure is the 
same as that of a solution containing a known weight of a solid whose 
molecular weight is known, the temperatures of the solutions being the 
same. Then the molecular weights of the solids will be to each other 
as the weights of equal volumes of the solutions. 

Molecular Weights by Depression of Freezing Point. It has been 
shown that when weights of substances proportional to molecular 
weights are dissolved in equal weights of the same solvent, they lower 
the freezing point of the solvent to the same extent. From this gen- 
eralization it is evident that the molecular weights may be determined. 
This method is called the cryoscopic method of determining molecular 
weights. 

Molecular Weights by Lowering Vapor Pressure. A precisely similar 
law holds with regard to the effects of a dissolved substance upon the 
vapor pressure of the solvent. When weights of substances propor- 
tional to molecular weights are dissolved in equal weights of the sol- 
vent they lower to the same extent the vapor pressure jof the solvent. 
This fact may also be used to determine molecular weights. 

Determination of Atomic Weights from Avogadro' s Law. 

From what has been said it is evident that the determina- 
tions of atomic weights by the methods thus far given were 
unsatisfactory because of our inability to decide as to the 
number of atoms entering the molecule. It will now be 
shown how we may obtain other information on this point. 



36 

Let its compare the gaseous compounds of the elements 
we are studying with each other. It is evident that a 
compound molecule must contain at least one atom of each 
constituent element, therefore, if we find the smallest weight 
of an element in any compound we shall have found its 
atomic weight. 

Take for example the compounds of hydrogen in Table I 
— in the first column are given the specific gravities, the 
doubles of these numbers in the second column give the 
molecular weights in microcriths, in the third column is 
given the per cent of hydrogen in the molecule, or the 
proportion which the weight of hydrogen, in the molecule 
bears to the whole weight of the molecule, in the fifth 
column this weight of hydrogen is given in m. c's. 





TAELE I. 










Specific 
gravi- 


Molecular 
•weight 


Proportion 
of hydrogen. 


Weight 
of H. in 


Symbols. 




ties. 


m m. c. 




m. c. 




Hydrochloric acid, 


18.25 


36.5 


•0274=3^ 


1 


HC1 


Hydro bromic acid. 


40.5 


81.0 


•0123-.V 


1 


HBr 


Water vapor, 


9.0 


18.0 


.1111=/* 


2 


OH, 


Sulphydric acid. 


17.0 


34.0 


.0588=^ 


o 


SH, 


Ammonia, 


8.5 


17.0 


.1765=tV 


3 


NH 3 


Phosphorus tri-hydride. 


17.0 


34.0 


.0882=^ 


3 


PH 3 


Harsh gas, 


8.0 


16.0 


.250 =& 


4 


CH 4 


defiant gas, 


14.0 


28.0 


.161 =^ 


4 


C 2 H 4 



It is thus seen that the smallest weight of hydrogen in 
any of these compounds is one m. c, and this is the smallest 
weight yet found in any compound. It also appears from the 
table that the amounts found in the other compounds are 

multiples of this small weight. 

TABLE II. 



Specific 


Molecular 


gravi- 


weight 


- 


in m. c. 


9 


18.0 


14 


28 


22 


44 


32 


64 


40 


80 


16 


32 



Proportion ™gM 



Symbols. 



Water vapor, 
Carbon monoxide, 
Carbon dioxide, 
Sulphur dioxide, 
Sulphur trioxide, 
Oxygen, 



.8889=11 

.5714=M 
.7272=ff 
•50 =ff 
•60 =M 

l.oo =u 



16 
16 

32 
32 

48 

Q9 



OH, 
CO 

co 2 

so; 
so; 
o, 



37 



TABLE III. 





Specific 
gravi- 


Molecular 
weight 


Proportion 
of CI 


Weight 
of 01. 


Symbols. 




ties. 


in m. c. 




m m. c. 




Hydrochloric acid, 


18.25 


36.5 


•9726= ||;| 


35.5 


HC1 


Acetyl chloride, 


39.2 


78.5 • 


.452 = ff:f 


35.5 


C 2 H 3 OCl 


Carbonyle chloride, 


49.5 


99.0 


.717 = U 


71 


COCl 2 


Phosphorus tri=chloride, 


68.7 


137.5 


77 4 — tor, 5 


100.5 


PClo 


Carbon tetrachloride, 


77 


154 


.922 =#£ 1 142 


cci, 


Chlorine, 


35.5 


71 


1.000 =fi 71 


CI 2 



A similar comparison of the compounds of oxygen and 
chlorine in Tables II and III, shows that the smallest amounts 
of these elements which enter are respectively 16 and 35.5 
microcriths, and no smaller weights have ever been found to 
enter; again, all larger amounts are multiples of these smaller 
weights. 

These facts lead irresistibly to the conclusion that these 
smallest weights are our chemical units or atoms, and the 
larger amounts are exact multiples because they contain two 
or more atoms. The law of Avogadro then gives us the 
means of deciding as to the molecular weights of gaseous 
substances and by a comparison of the various compounds 
we select the smallest weight of an element which enters any 
compound as the atomic weight. The number of times this 
weight is contained in the other molecules gives the number 
of atoms of the element which enter them. 

It can now be seen that had we not taken the weight of 
the half hydrogen molecule as the standard for molecular 
weights it would have been necessary to express the smallest 
amounts of hydrogen which enter certain compounds by %. 
Our standard m. c. is the smallest mass of matter which has 
yet been separated from any compound. It is the chemical 
atom, and since it is the half molecule, the molecule of hydro- 
gen -evidently contains two atoms. 

It should be remembered that the atomic weights depend 
upon the assumption that the same proportions which exist 
between the constituents of any compound, exist between the 



38 

constituents of the molecules of said compound. Such is 
the only rational assumption, and these atomic weights are 
the relative weights of the atoms or chemical units of dif- 
ferent substances, or the actual weights of the different 
atoms in terms of the weight of the hydrogen atom taken as 
unity. 

Compounds sometimes contain the elements in other pro- 
portions than that of atomic weights, but the variation from 
atomic proportions arises from the fact that molecules, as 
already stated, are formed by the union of an atom of one 
kind with one, two or three of another kind, or two of a kind 
with three of another, etc., etc. These different proportions 
are all combining or equivalent weights, and it is clear that 
they must be multiples or sub-multiples of the atomic 
weights. When elements unite in the proportion of one atom 
to one of another kind, the equivalent weights are the same 
as atomic weights, but they are different when the atoms 
unite in other proportions. 

The relations between specific gravities and adopted mole- 
cular weights are not usually so exact as is indicated in 
Tables I, II and III. The numbers here given (specific 
gravities) may be considered as corrected by the results of 
chemical analysis. 

From certain of their volatile compounds, by the applica- 
tion of Avogadro's law, the atomic weights of the following 
thirty-eight elements have been determined: 

Aluminum, antimony, arsenic, boron, bromine, bismuth, 
carbon, cadmium, chlorine, chromium, copper, fluorine, 
gallium, hydrogen, indium, iodine, iron, lead, mercury, 
molybdenum, nickel, nitrogen, osmium, oxygen, phosphorus, 
selenium, silicon, sulphur, tantalum, tellurium, thorium, 
titanium, tungsten, vanadium, zinc and zirconium. 

By this method alone four of the elements named (alum- 
inum, copper, gallium and iron) have atomic weights double 
those usually assigned them. 



39 



Number of Atoms in Elementary Molecules. When the 
atomic and molecular weights of an element are known it is 
evident that the quotient of the latter by the former gives the 
number of atoms in the molecule. The molecular weights of 
thirteen of the elements have been determined from their 
specific gravities in the gaseous state and thence the number 
of atoms in their molecules. The elements referred to are 
given in the subjoined table together with the relation 
between their atomic and molecular weights : 





Molecular Weight 


Elements. 


Atomic Weight 




Number of Atoms 




in Molecule. 


Cadmium, 


1 


Mercury, 


1 


Zinc, 


1 


Hydrogen, 


2 


Chlorine, 


2 


Nitrogen, 


2 


Tellurinm, 


2 


Oxygen, 


2 


*Bromine, 


2 


x Iodine, 


2 


x Selenium, 


2 


x SuIphur, 


2 


Phosphorus, 


4 


Arsenic, 


4 



It is thus seen that cadmium, mercury and zinc are monatomic and 
phosphorus and arsenic are tetratomic, the others were diatomic under 
the conditions of the experiments. Those elements marked with an 
asterisk varied in specific gravity with certain variations of tempera- 
ture. Thus, sulphur at a lower temperature had six atoms in a mole- 
cule and iodine at a higher temperature than that employed in the 
table had one atom in the molecule. 

Most of the elementary bodies thus appear to be diatomic. 
That this conclusion is involved in the law of Avogadro max 
also be seen from the following consideration. It is known 
that one volume of hydrogen combines with one volume of 
chlorine to form two volumes of PIC1 — from the law, each o\' 
the two volumes of HC1 contains as many molecules of 11(1 
as each of the original volumes contained molecules of H 



40 

and CI respectively ; now snppose that the volumes of H and 
CI each contain n molecules of H and CI respectively, the 
two volumes of HC1 must each contain n molecules, and as 
each molecule of HC1 must contain at least one atom of H 
and one of CI, there must have been at least 2n atoms of 
each of these elements, and consequently two atoms to each 
of the n molecules. In the same manner by considering' the 
fact that one volume of oxygen combines with two volumes 
of hydrogen to form two volumes of water vapor, we arrive 
at the conclusion that the molecule of oxygen contains two 
atoms and by similar considerations of certain of their com- 
pounds the molecules of nitrogen and sulphur may be shown 
to contain two atoms. 

These are unavoidable conclusions from the law of Avogadro, but 
there is also some independent evidence that certain molecules of ele- 
ments contain two atoms. Thus it was found that carbon burned in 
the protoxide of nitrogen produces more heat than when burned in 
oxygen. A natural explanation of this fact is found in the supposition 
that it requires more heat to decompose the molecule of oxygen (it 
being composed of two atoms) than it does to decompose the molecule 
of the protoxide of nitrogen. Again, the nascent state which has been 
referred to as favorable to chemical action may be conceived to be due 
to the uncombined condition of the elementary atoms when just liber- 
ated from some previous combination. Thus, when hydrogen gas is 
passed through nitric acid it produces no chemical change. The 
molecules above referred to each have two atoms, but such is not the 
case with all elementary molecules. 

Again, the relations between the specific heats of gases at a constant 
volume and a constant pressure are not exactly what they should be 
from a consideration of the external work done ; it requires more heat 
to raise the temperature of a gas under constant volume than it 
should, in proportion to that required under constant pressure. Now 
it may be supposed that a portion of the heat is consumed in the first 
case in producing a motion among the particles of the molecules which 
does not appear as change of temperature, and if the supposition be 
correct then the discrepancy referred to should not be observed in a gas 
whose molecule contains one atom. The relation between the specific 
heat of mercury vapor at a constant pressure and constant volume 
was found to accord exactly with theory, which seems to be a physical 
proof that the mercury molecule has but one atom. 



41 

Isomorphous Relations. Bodies which crystallize in the 
same or in very similar forms are said to be isomorphous, 
and the fact that many compounds of similar chemical 
constitution do crystallize in the same form led some 
chemists to believe that the same crystalline form assured 
the same atomic constitution of the respective molecules of 
the substances, that an equal number of atoms arranged in 
the same way or united in the same way, gave the same 
crystalline form. 

It is now known that when the term isomorphism is used 
in the above sense the conclusion is not warranted. If in 
addition to the same crystalline form we impose the con- 
dition that the bodies under consideration must be capable 
of replacing each other in the same crystal without destroy- 
ing the form, the idea of isomorphism becomes much more 
restricted and the conclusions which result from its applica- 
tion in fixing atomic weights are generally satisfactory. 
Thus, it is known that aluminum and oxygen unite in only 
one proportion, 18.3 of aluminum to 16 of oxygen, but this 
same proportion exists in the numbers of 

aluminum and OXYGEN. 



36.6 


32 


54.9 


48 


73.2 


64 



and the atomic weight assigned to Al will depend upon the 
constitution assigned to the oxide — if the oxide be a 

OXYGEN. ALUMINUM. 

monoxide we shall have Al O 16 18.3 

dioxide we shall have Al 2 32 36.6 

trioxide we shall have Al O a 48 54.9 

sesquioxide we shall have Al 2 Oa 48 ] wi\ 

The numbers in the last column are the weights which 
must be assigned to the atom of aluminum according to the 
several modes of constitution indicated in the first column. 



42 

The constitution of the oxide alone does not enable us to 
deeide between the different formulas, but as the aluminum 
oxide is isomorphous with the sesquioxide of iron it is 
assumed to be a sesquioxide and its atomic weight thus 
becomes fixed as 27.4. 

The utility of this law is limited in application to groups 
of closely allied substances and its indications become more 
valuable when connected with conclusions from other 
physical laws. The law of isomorphism was first enunciated 
by Mitscherlich in 1819. 

Yolume Relations of Elements and Compounds. Under 
the law of Avogadro we have seen that when hydrogen is 
used as the standard for specific gravities and the half 
hydrogen molecule as the standard for molecular weights, 
the specific gravities of gases are the halves of their mole- 
cular weights. As most elementry gases are diatomic it 
follows that the atomic weights and specific gravities of 
elementary gases are given by the same numbers — one-half 
their molecular weights. Since specific gravities are given 
by the weights of equal volumes it follows that equal 
volumes of elementary gases contain atomic proportions by 
weight. Atomic proportions being the proportions which 
combine it likewise follows that the combining volumes of all 
diatomic elementary gases are equal, and if we conceive the 
smallest combining volumes of such gases to contain only 
one atom we reach the conclusion that the ultimate combining 
volumes of elementary gases occupy equal spaces, or atoms of 
elementary gases occupy equal spaces. From the above 
relations it is readily seen that the number of volumes of the 
diatomic elementary gases which combine to form a com- 
pound gas are indicated by the number of atoms of each 
element which enter the molecule of the compound gas. 
Thus, to form 

HCl there are required 1 vol. H and one vol. CI 

NH 3 there are required 1 vol. N and three vols. H 

OH 2 (water vapor) there are required 1 vol. O and two vols. H 



43 

Research widely extended has proven that with a few 
exceptions, which may yet disappear, the molecules of com- 
pound gaseous bodies occupy twice the space of the hydro- 
gen atom, no matter how many atoms of the elementary 
gases enter the compound molecule. Thus, each of the 
molecules HO, NH 3 , CH 4 , C 2 H 4 , CO, &c, occupies twice the 
space of the hydrogen atom. 

Since the same proportions exist between the quantities 
of the elements which form the whole body as do be- 
tween the quantities which form the molecule, it follows 
that no matter how many volumes of elementary gases com- 
bine to form a compound gas of the first order, they are all 
condensed to two volumes in the compound. All molecules, 
whether of the first or a higher order, occupy equal spaces, 
hence the same law of condensation holds in combinations 
of higher order than the first. 

This law of condensation is illustrated in the examples 
below. 

2 vol. H +1 vol. O give 2 vol. water vapor = OH 2 

2 vol. CI +1 vol. O give 2 vol. hypochlorous anhydride = C1 2 

2 vol. N +1 vol. O give 2 vol. nitrogen protoxide = N 2 

1 vol. CI + 1 vol. H give 2 vol. hydrochloric acid gas = HC1 

1 vol. N +3 vol. H give 2 vol. ammonia = NH 3 

2 vol. CO + 2 vol. Clgive 2 vol. carbonyl chloride = COCl 2 

2 vol. C 2 H 4 + 1 vol. O give 2 vol. ethene oxide = C, H , O 

Apparent Exceptions to the Law of Volumes. — From the 
foregoing considerations it is seen that the molecules of 
gaseous bodies are believed to occupy equal spaces, twice the 
space occupied by the hydrogen atom, and that their vapor 
densities referred to hydrogen are the halves of their mole- 
cular weights. There are a few apparent exceptions to this 
law, but the exceptions are believed to be due to molecular 
changes which take place in the bodies under the influenceof 
heat during the determination of their vapor densities, and 
that there is no occasion as yet to doubt the validity of 



44 



Avogadro's law. Among the bodies which were first thought 
to be exceptions may be mentioned 

PCls, NLLC1 and C 2 H 4 2 . 
The quotient obtained by dividing the atomic weight of a 
simple body by its density is called the atomic volume, and 
that obtained by dividing the molecular weight of a body by 
its density is called the molecular volume. If matter were 
continuous these quotients would give the relative volumes of 
atoms and molecules. 

Specific Heats and Atomic Weights. The investigations 
of Pettit and Dulong in relation to the specific heats of the 
solid elements developed the fact that their specific heats are 
very nearly inversely proportional to their atomic weights, so 
that if atomic proportions, by weight, of these different 
elements be taken the quantity of heat to change the temper- 
ature of these proportions through equal intervals is the 
same in all. 

In the following table a number of the solid elements are 
arranged according to their determined specific heats, begin- 
ning with those having the greatest: — 





H 


A 


HX A 


Lithium, 


0.941 


7 


6.6 


Sodium, 


0.293 


23 


6.7 


Aluminum, 


0.214 


27.4 


5.9 


Potassium, 


0.166 


39 


6.5 


Iron, 


0.114 


56 


6.4 


Nickel, 


0.109 


59 


0.4 


Copper, 


0.0952 


63.4 


6.0 


Zinc, 


0.0955 


65.2 


6.2 


Silver, 


0.0570 


108 


6.2 


Tin, 


0.0562 


118 


6.6 


Gold, 


0.0324 


197 


6.4 


Platinum, 


0.0324 


197.4 


6.4 


Lead, 


0.0307 


207 


6.4 



In the 1st column are the specific heats, in the 2nd the 
atomic weights and in the third the product of these num- 
bers; water is taken as the standard of specific heats. This 
table exhibits the inverse relation existing between atomic 



45 

weights and specific heats and the products all fall between 
the numbers 5.4 and 6.9 — the mean value when all the solid 
elements are considered is usually given as 6.4. It is true 
that there are variations from this number but the variations 
are slight and are probably due to the causes which influence 
the thermal condition of bodies and render the exact determ- 
ination of specific heats uncertain. 

Since the announcement of Pettit and Dulong in 1819, 
that the atoms of all elements have the same capacity for 
heat, or the same specific heat, many facts have been accum- 
ulated in favor of the generalization and render it very 
probable that it is correct. 

This number (6.4) is frequently called the atomic heat of 
elements. 

This law gives us a ready means for the determination of 
the atomic weights of elements when their specific heats are 
known, it being only necessary to divide the number 6.4 by 
the specific heat. However, the difficulty of determining 
specific heats accurately, limits very much this method of 
arriving at atomic weights, but the law enables us to decide 
with certainty between two or more possible hypotheses. 

We have seen that analysis will give the proportions of 
the constituents of a compound with a great degree of 
accuracy and if we can decide as to the number of atoms of 
the respective elements in the compound the atomic weights 
become known, e. g.: analysis shows that silver chloride con- 
tains 108 parts of silver and 35.5 parts of chlorine — with only 
this fact we can not tell whether there be one or more atoms 
of silver, but by dividing 6.4 by the specific heat of silver 
(.057) we get 112 a number so nearly coinciding with the 
result of analysis as to show beyond doubt that there is but 
one atom. As the result of analysis is more reliable than 
the determination of specific heat we accept 108 as the weigh! 
of the atom of silver — the specific heat merely deciding us as 
to the number of atoms in the compound. 



46 



The specific heats of the elementary bodies have not been 
determined at any common temperature, so that the values 
found are not strictly comparable. The specific heats of the 
elements generally vary with the temperature, but there are 
certain temperature-intervals, different for the different 
elements, between the limits of which the specific heats are 
nearly constant. For this interval only is the law of Dulong 
and Pettit true. 

The following forty-nine solid elements have had their 
specific heats determined directly : 



Aluminum 


Cobalt 


Magnesium 


Selenium 


Antimony 


Copper 


Manganese 


Silicon 


Arsenic 


Didymium 


Mercury 


Silver 


Boron 


G-allium 


Molybdenum 


Sulphur 


Beryllium 


Gold 


Nickel 


Sodium 


Bismuth 


Indium 


Osmium 


Tellurium 


Bromine 


Iodine 


Palladium 


Thallium 


Carbon 


Iridium 


Phosphorus 


Thorium 


Cadmium 


Iron 


Platinum 


Tin 


Calcium 


Lanthanum 


Potassium 


Tungsten 


Cerium 


Lead 


Rubidium 


Uranium 


Chromium 


Lithium 


Ruthenium 


Zinc 
Zirconium 



With but few exceptions the product of the specific heat 
into the atomic weight is approximately equal to 6.4, all fall- 
ing between 6 and 7. The exceptions are boron, beryllium, 
carbon, gallium and silicon. 

The application of the law of equal atomic heats has been found in 
many instances to extend to chemical compounds in the case of bodies 
of similar atomic composition. In such cases the products of the 
specific heats into molecular weights are nearly constant and are equal 
to as many times 6.4 as there are atoms in the molecule. If the law 
were of general application to compounds it would give us obvious 
means for the determination of the number of atoms in a molecule and 
a method of general application in determining atomic weights. But 
the law is not of general application to compounds and can only be 
used to a limited extent in determining atomic weights. 



47 

In the case of the solid elements when their specific heats are deter- 
mined under specified conditions it may be considered that there arc no 
exceptions to the law of Pettit and Dulong, so closely do the products 
of the atomic weights and specific heats approximate to a common 
number. The difficulty of determining: how much of the heat trans- 
ferred to gases and compounds is consumed in performing internal and 
external work and how much in simply affecting temperature, renders 
it as yet impossible to bring them under the general law. It is a 
reasonable expectation that this will be done as our knowledge of 
molecular structure increases. 

VALENCY OR QUANTIVALENCE. 

We have already seen that the atomic and equivalent 
weights of some of the elements are the same, and in others 
that the atomic weight is some multiple of the equivalent 
weight. In other words that atoms of certain elements can 
only replace or combine with atoms of other elements in the 
proportion of one to one, in other cases this equivalency or 
substitution can occur in the proportion of one atom to two 
or more of another kind — thus, chlorine, bromine and iodine 
always combine with hydrogen in the proportion of one atom 
to one, oxygen and sulphur one atom to two of hydrogen, 
and when sodium acts on hydrochloric acid each atom of 
sodium replaces one of hydrogen, as Na+HCl=NaCl+H, 
with zinc under the same circumstances each atom replaces 
two of H, as Zn+2HCl=ZnCl 2 +H 2 . This difference of 
combining or replacing power has been called vale ncy, 
quantivalence and atomicity. The first term is deemed best 
and will be adhered to — the second may be used with pro- 
priety — but the third should not be used in this sense. 

If we select the hydrogen atom as the standard of refer- 
ence the valency of any other element is known by the 
number of hydrogen atoms that its atom is equivalent to in 
the sense just given. The elements have been classed 
according to degree of valency as univalent, bivalent, trival- 
ent, &c, and are also called monads, dyads, triads, tetrads, 
pentads, &c The elements of even valency are also called 
artiads and those of uneven valency perissads. The valency 



48 

is sometimes indicated by putting dashes or Roman numerals 
after the symbols of the elements, thns — O n , C IV , P v , &c. 

Another method of indicating the valencies of elements 
and the manner in which they are supposed to be satisfied in 
combination is by graphic formulae thns, water may be rep- 
resented by 

H— 0— H 

and carbon dioxide by 

o=c=o, 

marsh gas by 

H 

I 
H— C— H. 

I 
H 

These are called graphic or structural formulae and indicate 
nothing more than the degree of valency of the elements 
and the manner in which they may be supposed to be sat- 
isfied in combination. 

The valency of an atom as shown by its replacing power 
corresponds exactly with that shown by its combining power 
— that is, an atom capable of replacing a certain number of 
monad atoms is also capable of combining with the same 
number — thus the atom of zinc which is capable of replacing 
two atoms of hydrogen is also capable of combining with 
two atoms of CI, or Br — monad elements. This property of 
valence is inherent to radicals, already defined, as well as to 
elements, and is manifested when they change places in 
reactions with other radicals or elementary atoms; some 
radicals are capable of combining with or replacing one 
monad atom and others more than one. 

In the above graphic formulae it is seen that the units of 
valency of each atom are represented as satisfied by com- 
bination with units of valency of other atoms; such com- 
pounds are called normal or saturated compounds and in the 
molecule of such a saturated compound the sum of the 
perissad atoms is always an even number. This is the Law 



49 

of even numbers and it is of necessity true in saturated 
compounds, from the above definition of such compounds. 
To form a saturated molecule it is not however necessary 
that the units of valency of each atom shall combine with 
the units belonging to atoms of different elements, they 
sometimes combine with those of other atoms of the same 
element, thus — 

c — c c — c — c 

III III III . II III 

H3 H 3 H 3 H 2 H 3 

which are saturated hydro-carbons.* 

By considering the above formulae it is evident that if an 
atom of any kind could be removed the balance of valency 
would be destroyed and a certain number of units of valency 
would be left unsatisfied — thus if from the saturated mole- 
cule CH 4 we remove one atom of H, we get the compound 
CH 3 , from S0 3 remove one atom of O and we get S0 2 . These 
unsaturated molecules constitute the compound radicals 
already referred to and the valency of a compound radical 
may generally be said to equal the valency of the atom or 
atoms which the saturated molecule may be considered to 
have lost. As already stated, it is only a few of these non- 
saturated molecules that exist in a free state, as CO, S0 2 , 
&c, in other cases two of the unsaturated molecules combine 
with each other, and then again they appear as transferable 
compounds in chemical reactions without isolation. The 
tendency of unsaturated radical molecules to combine with 
each other seems to be analogous to the action of the atoms 
of elementary bodies — since we have seen that these ele- 
mentary atoms seldom exist in the free state but are com- 
bined in pairs. It may also be stated that generally the 
combined radicals which exist separately have an even 
valency. 

*It is evident from this consideration that there is a lack of pre- 
cision in the definition of a "saturated molecule." Other definitions 
have been proposed but are upon the whole not more satisfactory. 
4 



50 

Variable Valency. The valency of an element is not a 
fixed and unvarying property. Many of the elements exhibit 
varying" degrees of valency as is especially shown by their 
varying degrees of combining power — thus tin forms two 
compounds with CI — viz.: SnCl 2 and SnCh and phosphorus 
forms PC1 3 and PC1 5 , numerous other examples might be 
given. Compounds formed under these varying influences 
are often as different from each other as are the compounds 
of different elements and hence arises the difficulty of 
classifying the elements according to their valency. How- 
ever, of the different degrees of valency shown by the same 
element some one degree is generally more common and the 
compounds resulting from its action more permanent than 
any other and in several elements, as H and the alkaline 
metals, the valency has been found invariable. 

Of the multivalent elements the variation in valency 
usually takes place by a loss or gain of two units of valency, 
so that the possible conditions of the same element are 
usually all even or all odd, thus, CI may be univalent, 
trivalent, quinquivalent and septivalent. 8 may be bivalent, 
quadrivalent or sexvalent. 

It is at present impossible to account for these variations but as a 
general rule the compound in which the valency of a polygenic element 
is most completely satisfied is the most stable and the others tend to 
pass into this one. From these considerations it is evident that the 
valencies of most of the elements are not fixed and the conditions of 
the variations are not known. From a consideration of all the facts 
the most logical conclusion is that the valency is, like affinity, a 
relative property of the atoms, depending upon a variety of causes, 
among which may be classed the mutual influence of the atoms on 
each other, the relative quantities of the acting substances and the 
temperature. It may also be observed that the theory of valency 
reiterates the law of multiples, which is the simple statement of an 
experimental fact. 

Valency and Affinity. Valency and affinity are properties 
inherent in the atoms and as yet understood, are distinct and 
different properties. Affinity has reference to the force with 
which atoms or molecules attract each other and is approxi- 



51 

mately estimated by the thermal effects of their combina- 
tions. Valency has reference only to the saturating capacity 
in combination or replacement and irresistibly introduces 
the idea of arrangement of atoms in the molecule. 

The abstract idea of valency has reference only to the numerical 
capacity of saturation, but the concrete conception sees each body 
characterized by a particular order in combination and every molecule 
of a definite structure. The theory of valence then finds application 
in expressing the relations between the atoms of molecules and in 
allowing conception of the relative constitution of bodies. Again, 
from knowledge of the more common valency of elements the theory is 
of great importance in expressing all ordinary reactions, the results of 
the general laws of combination. 

RELATIONS BETWEEN THE ATOMIC WEIGHTS AND 
PROPERTIES OF THE ELEMENTS. 

Although atoms are hypothetical masses and are beyond direct 
observation, their relative weights, as has been stated, are the con- 
stants of chemistry and are indispensable to analysis and stochiome- 
trical research. It now seems possible that these numbers may become 
equally important in all branches of physical science, for recent investi- 
gations point to an interdependence, more or less complete between the 
atomic weights and physical properties of the elements. In 1815, Prout 
brought forward the view that the matter of which all elements are 
composed is hydrogen and that the atomic weights of all other 
elements are entire multiples of the atomic weight of hydrogen and 
this has been known as Prout's Law. 

The investigations of Stas of Brussels, undertaken for the purpose 
of testing Prout's Law are frequently held to invalidate it, but so 
large a majority of the atomic weights are so nearly exact multiples of 
that of hydrogen, that it can hardly be the result of chance, and 
Prout's view is still believed by many chemists to have a high degree of 
probability. It has also been long known that the atomic weights of 
many allied elements have certain simple numerical relations, but New- 
lands was the first to point out the fact that the elements, when 
arranged in numerical order of their atomic weights, exhibit a periodic 
recurrence of similar properties. This Law of Periodicity may be 
illustrated by a consideration of the first fourteen elements after hydro- 
gen, and is most evident if we consider the atomic volumes of the solid 
elements in connection Avith their atomic weights. 

The atomic volume, as already stated, is obtained by dividing the 
atomic weight by the density of the clement. The elements referred to 
are here arranged in order of their atomic weights and immediately 
beneath each is written its atomic volume, then its density. 



Li = 7 Gl = 9.0 


Bo=n 


C=12 


X=14 


0=16 


V =11.9 5.6 


4.0 


3.6 


o 


o 


D = 0.59 1.64 


2.6s 


3.3 






Na =23 Mg=24 


Al =27.3 


Si=2S 


P=31 


S=32 


V =24 14 


10 


11 


16 


16 



52 

Fl=19 

o 

Cl=35.5 
27 
D =97 1.75 2.67 2.49 1.S4 2.06 1.38 

The atomic volumes of the elements thus gradually decrease tow- 
ard the middle of the series and then increase. The densities of the 
elements increase toward the middle and then decrease. The volatili- 
ties of the elements also diminish toward the middle and then increase. 
The more common valencies of the elements increase toward the mid- 
dle of the series and then decrease. In addition to these properties 
others, as the malleability, fusibility, conductivity, refractive power 
and heat of combustion, also apjjear to be closely connected with their 
atomic weights. Mendelejeff and others have shown that the entire 
list of elements can be thus arranged in series and that the properties 
of the elements are in periodic relations with their atomic weights. 
The classification of the elements cannot be properly discussed without 
a fair knowledge of the subject matter of chemistry, and this discus- 
sion is accordingly not essential to that knowledge, but the proba- 
bilities in favor of the Periodic Law are great, and it promises, at no 
distant day, to furnish a new basis for physical investigation as well 
as for a classification of the elements. 

STOCHIOMETRY. 

That class of chemical computations which can be made 
from a consideration of the numerical relations of atomic 
weights and the volume relations of elements and compounds 
is called stochiometrical. From a knowledge of preceding 
principles many such computations are possible. It has 
already been stated that the symbols of the respective 
elements represent atoms and that the atoms of different 
elements have cliff erent weights — that the molecular weights 
of substances are the sums of the weights of the atoms in 
their respective molecules. In the most limited sense chem- 
ical symbols represent atomic weights of their respective 
elements in terms of the weight of the H atom, but in a more 
general sense, in all equations, reactions and formula^ they 
stand for quantities proportional to atomic weights and when 
the amount by weight of any one element in a formula or 



53 

equation is given the amounts of all the others become 
known. 

Percentage Composition. Thus, the formula for water is 
OH 2 and from the relations expressed in the formula if either 
the amount, of H or O is assumed the amount of the other 
element is also known. 

From the formula of a substance it is evident that we 
may also readily compute its percentage composition — thus, 
the formula of alcohol is C 2 H 6 — the molecular weight is 46, 
hence in 46 parts by weight of alcohol there are — 24 of C 

6 of H 
16 of O 

46 
hence in 100 parts we should have 

for C 46 : 24: :100 : x= 52.18 
for H 46 : 6: :100 : y= 13.04 
for O 46 : 16: : 100 : z= 34.78 



100.00 
Having given the percentage composition of a substance 
we can also readily determine the numerical relations exist- 
ing among the atoms but not necessarily the actual number 
of atoms in the molecule — thus the percentage composition 
of acetic acid is C = 40 

H = 6.67 
O = 53.33 



100.00 
since these numbers are the relative weights of the elements 
in the substance if we divide them by the atomic weights the 
quotients will express the relations existing among the num- 
bers of atoms of the different elements. Performing the 
division referred to we have for the numerical relation of 
atoms 

Kj-i.M 0.6.67 Os.33 



54 

which is evidently the same as 

Ci H 2 Oi. 

Empirical and Molecular Formulae. The simplest expres- 
sion for the numerical relations existing among atoms of a 
molecule of a substance is called its empirical formula; that 
is to say, when we express the numerical relation among the 
atoms by the smallest numbers possible ; thus above CiH 2 Oi is 
the empirical formula for acetic acid. The same relations 
exist among the numbers of atoms whether the formula be 
GH 2 Oi, C 2 H 4 2 , or C 3 H 6 3 , &e. 

The formula which gives the exact number of atoms of 
each of the elements which enters the molecule of a sub- 
stance is called the molecular formula. It can not be com- 
puted with certainty from the percentage composition alone, 
but if the molecular weight of the substance is known the 
problem admits of definite solution, for from the molecular 
weight we know the sum of the atomic weights and can 
decide which of the formulae expressing the numerical rela- 
tions among the atoms is the molecular formula. 

Thus, in the example above the molecular weight of the 
acetic acid is 60, hence it is evident that of the possible 
formulae C 2 H 4 2 is the molecular formula of the acid. The 
molecular formula is always the same as, or a multiple of, 
the empirical formula. 

Problems Inyolving Weights. Since, as has been said, in 
the most general sense the symbols represent quantities pro- 
portional to atomic weights and formulae represent quantities 
proportional to molecular weights it is easy to determine the 
amounts of the various substances indicated in any equation 
when the amount of any one is assumed. For this purpose it 
is only necessary to express the atomic and molecular 
weights of the different terms of the equation and simple 
proportions will solve the problem. 
Thus, in the equation 

Zn+2HCl=ZnCl 2 +H 2 . 



55 

expressing* the action of Zn upon HC1, suppose we assume 
that Zn stands for 10 ounces of zinc — then to determine how 
much HC1 is indicated we proceed as follows: the atomic 
weight of Zn=65.2 and the molecular weight of HC1=36.5. 
The reaction indicates that for the transformation of 65.2 
parts of Zn there are required 2x36.5=73.0 parts of HC1 — 
hence the amount to transform 10 parts of Zn would be 
determined by the proportion 

65.2 : 73 : : 10 : x. 
The amounts of the other substances involved in the reaction 
under the supposition that 10 ounces of zinc are employed 
would be determined in exactly the same manner. 

It matters not whether some of the terms of the equation 
are simple atoms or whether all the terms are composed of 
molecules. The molecular and atomic weights of the 
different terms express the relations existing between the 
amounts of the substances employed in the reaction and from 
these relations the amounts of all the substances indicated 
can be determined when the amount of any one is assumed. 

Problems Involving Volumes. All of the above solutions 
depend upon the numerical relations of atomic weights but a 
chemical equation expresses not only relative weights but 
also relative volumes of the reagents and products when in 
a state of gas. We have seen that all gaseous molecules 
occupy equal spaces and that gaseous atoms occupy one half 
the space of the molecule, coupling these facts with the 
principles of notation explained it is evident that the relative 
numbers of volumes in an equation of gaseous terms can be 
read off directly — thus 

2CO+0 2 =2C0 2 
and 

CH 4 +0 4 =C0 2 +2H 2 0. 
In the first equation, since molecules occupy equal spaces, it 
is seen that the number of volumes of CO a is the same as the 
number of volumes of CO and the number of volumes of O 



56 

involved is one half that of the other gases. — In the second 
equation the relative volumes are, one of CH 4 , two of O, one 
of C0 2 and two of OH 2 (vapor of water). 

It is often desirable to pass from volumes to weights or 
the reverse in the case of gaseous bodies. The problem is so 
simple as to require only the statement that in the first case 
we multiply the number of volumes by the weight of a unit 
of volume and in the second case we divide the weight by 
the weight of a unit of volume; volumes, of course, being 
always taken under standard conditions of temperature and 
pressure. 



CHEMISTRY OF THE NON-METALS AND 
THEIR COMPOUNDS. 



OXYGEN. 

Oxygen is the most abundant and widely distributed of 
the chemical elements. It exists in the uncombined state in 
atmospheric air forming" about one-fifth of its volume ; it is 
there mixed with nitrogen which constitutes nearly the entire 
bulk of the remaining four-fifths. 

In the free state oxygen is an essential to all forms of life. 

In the combined form it is an important constituent of 
most of the mineral and organic substances. In this form it 
constitutes eight-ninths, by weight, of water and about one- 
half, by weight, of silica and of the various silicates and 
limestones, which compose by far the greater portion of the 
earth's crust. 

Oxygen was discovered by Priestly in England in 1774 
and called by him dephlogisticated air. In the folio wing- 
year it was independently discovered by Scheele in Sweden. 
It was named oxygen by Lavoisier. 

Physical Properties. Oxygen is a gas tasteless, odorless, 
colorless, and perfectly transparent. It is slightly soluble, 
water at 60° F. dissolving about .03 of its volume. By great 
pressure and low temperature it has been liquefied and by 
further cooling solidified. Its specific gravity referred to 
hydrogen is given by its atomic weight; it is thus seen to be 
slightly heavier than atmospheric air; when liquefied it is 
lighter than water. 



58 

Chemical Properties. Oxygen is remarkable for the wide 
range of its chemical action. With the exception of bromine 
it forms compounds with all other elements and with the 
exception of six elements it unites directly (that is without 
the intervention of a third substance). 

These combinations as already stated are called oxides 
and the process is termed oxidation. 

The combination of oxygen with the other bodies is 
always accompanied by the development of heat but if the 
oxidation is very slow the heat may not be perceptible. If 
the oxidation be sufficiently rapid to produce light and heat 
it becomes a case of combustion. 

Combustion in a general sense is any chemical action 
accompanied by heat and light ; all ordinary cases of com- 
bustion in air are processes of oxidation, the light and heat 
being the result of the chemical union of the oxygen with the 
body burned. In most cases an elevation of temperature is 
necessary to bring about the union of oxygen with other 
substances; with some bodies at ordinary temperature it 
unites slowly without sensible elevation of temperature, and 
with a few rapid oxidation takes place producing com- 
bustion. 

Action on Non-Metals. Among the non-metals phos- 
phorus is the only element that combines with oxygen at 
the ordinary temperature. In the air it gives off white fumes 
and emits a pale phosphorescent light. It is then under- 
going oxidation and if it be finely divided true combustion 
will result. This may readily be accomplished by dissolving 
a little phosphorus in carbon disulphide and pouring the 
solution on blotting paper; when the solvent evaporates, the 
finely divided phosphorus exposes a large surface to the 
action of the air, and the paper being a bad conductor the 
temperature rapidly rises and brilliant combustion results. 
In warm air a very slight elevation of temperature will cause 
phosphorus to burn and this is sometimes brought about by 



59 

the oxidation of the outside particles; phosphorus must 
accordingly be handled with great care. 

Phosphorus produces a bright light when burning in the 
air but the brilliancy is greatly increased when it is burned 
in pure oxygen due to the more rapid combustion and 
consequent higher temperature. 

All substances which burn in air burn far more readily in 
pure oxygen. By the combustion of phosphorus in air phos- 
phoric oxide is produced (P 2 5 ) which may be seen to rise 
in clouds from the burning phosphorus. This oxide is readily 
absorbed by water forming phosphoric acid. 

If a piece of wood charcoal be heated to redness at a 
single point and be plunged into a jar of oxygen brilliant 
combustion takes place, the oxygen combining with the car- 
bon producing carbon dioxide (C0 2 ) which is a colorless gas. 
Pure carbon has to be heated very highly before it will com- 
bine with oxygen and then the combustion is unattended with 
flame. 

Sulphur burns in air with a blue light when its tempera- 
ture is raised to about 500° F. In pure oxygen the brilliancy 
is much increased ; in each case the product of combustion is 
sulphur dioxide (S0 2 ) which readily unites with water form- 
ing sulphurous acid. 

Action on Metals. Several of the alkaline and alkaline 
earth metals (potassium, sodium, lithium, barium, calcium, 
and strontium) are readily oxidized in the air. 

Other of the common metals as iron, lead, and mercury 
are scarcely acted upon by dry air, and gold, silver, and 
platinum not at all. Under the influence of high temper- 
ature many of the metals burn readily. A magnesian ribbon 
will burn in air if the end of the ribbon be heated in a Bun- 
sen burner; the light is almost insupportable to the eye. 
The burning of iron is also easily accomplished and is best 
shown in a small way by wrapping one end of a softened 
steel watch spring spirally around a little cylinder of char- 



60 

coal and attaching the other end to a suitable holder, igniting 
the charcoal and plunging the whole into a jar of oxygen. 
It burns very brilliantly sending off a shower of sparks. 
The black oxide of iron Fe 3 4 is produced by the combus- 
tion. 

Zinc may be burned by a precisely similar arrangement 
giving (ZnO) zinc oxide. 

Iron can be prepared in such finely divided form that 
when exposed to air it will take fire spontaneously; it is then 
called pyrophoric iron. 

The preceding illustrations which might be extended 
indefinitely are all cases of oxidation, and it is seen that 
oxidation may or may not produce the phenomenon of com- 
bustion. All ordinary combustion in air is but the oxidation 
of the body burned, oxygen being the sustaining principle of 
such combustion and also of animal life. All bodies which 
burn in air burn with increased splendor in pure oxygen. 

It is well here to recall the important fact already stated 
that the oxides of the non-metals are generally acid oxides 
and of the metals basic oxides. The former when acted upon 
by water give the substances which we have defined as acids 
and the latter tend to neutralize these acids. So general is 
this tendency of the metallic oxides that any substance which 
forms a basic oxide may be defined as a metal, though it is 
not decided that every metal forms a basic oxide. 

Preparation of Oxygen. For laboratory and experimental 
purposes oxygen is most readily prepared from potassium 
chlorate (KC10 3 ) or manganese dioxide (Mn0 2 ). From either 
of the substances oxygen may be obtained by heating in 
suitable apparatus the results being indicated by the follow- 
ing reactions; KC10 3 (heated) =KCl+0 3 , 3Mn0 2 (heated) = 
MntOt+Oi. 

To accomplish these results a higher degree of heat is 
required than is convenient and it is customary and advisable 
to mix with the chlorate from one-fourth to one-fifth its 




F.G.I. 

Prepay 
P. F u „ 

fa. Bel 



61 

weight of the oxide when the liberation of oxygen takes 
place at a lower temperature than when either substance is 
used alone. The mixture of potassium chlorate and man- 
ganese dioxide may be heated in a glass retort or Florence 
flask, the retort or flask being closed by a perforated cork 
into which fits a short glass tube. A rubber tube connects 
with the glass tube and serves to convey the gas to a gas 
holder or to a jar filled with water standing on a bee-hive 
shelf. The manganese dioxide, or pyrolusite as it is called 
in mineralogy, is not changed in this operation. The action 
of the manganese dioxide comes under the term of catalytic 
action and is not thoroughly understoood but the oxide prob- 
ably passes to a higher state of oxidation and is then 
reduced. 

Oxygen may also be prepared by the decomposition of 
water (H 2 0) by electricity. In some laboratories both 
oxygen and hydrogen thus obtained are kept on hand in 
large holders, the electricity being supplied by dynamo- 
machines. 

Oxygen may be prepared on a large scale directly from the atmos- 
phere by passing a current of air over a mixture of caustic alkali and 
manganese dioxide ; alkaline manganates are thus formed. By passing 
steam over the heated manganates they are resolved into the original 
constituents with the liberation of oxygen. The operation can be 
made continuous. 

There are many other methods by which oxygen may be prepared. 
Priestly when he discovered oxygen obtained it from the red oxide of 
mercury. 

OZONE. 

Ozone was discovered by Schonbein in 1840. It appears to be a 
modified form of oxygen in which it is believed that there are three 
atoms in the molecule instead of two as in ordinary oxygen. Accord- 
ing to Avogadro's law it should be one and a hall' times as heavy as 
common oxygen and this has been determined to be the case by exper- 
iment. It exists in very small quantity in the atmosphere and is found 
in the purer air of the country or the seaside more than in thickly pop- 
ulated places. It has been estimated to constitute not more than one 
volume in a million volumes of air. 



62 

Physical Properties of Ozone. Under ordinary conditions ozone is 
a transparent gas showing a bine tinge when viewed along a glass 
tube a meter in length. The color deepens by pressure. The gas has 
a peculiar and distinct odor. It is more easily liquefied than pure 
oxygen and the liquid has a blue color. When heated to 300° F. ozone 
is converted into oxygen with an increase of half a volume. 

Chemical Properties. Ozone is chemically much more active than 
oxygen combining with many substances that oxygen will not affect. 
It will decompose potassium iodide liberating the iodine. In the pre- 
sence of alkalies it will unite with nitrogen and convert it into nitric 
acid. It will oxidize silver and also a solution of indigo, bleaching the 
latter; ordinary oxygen does not act upon these substances. Ozone 
acts upon many organic substances and it is to this fact that its bene- 
ficial effect in the air is attributed. In most cases of oxidation the 
remaining oxygen appears to be the same in volume as the original 
ozone. Air highly charged with ozone can not be breathed with im- 
punity, its action on the system resembling that of chlorine. 

Preparation of Ozone. Ozone is produced by the passage of electric 
sparks through the air or oxygen and is generally observed by its odor 
when a spark electric-machine is operated in the air. It is also pro- 
duced during the decomposition of water by electricity, by the slow 
oxidatioD of phosphorus and turpentine in the air. This latter fact has 
been suggested as an explanation of the acknowledged salubrity of 
pine regions. 

The presence of ozone may be detected by bringing into it a piece 
of paper moistened with a solution of starch and potassium iodide; 
the ozone liberates the iodine which gives a blue color with the starch. 
The test however does not insure the presence of ozone as certain other 
substances will have the same action, among these are chlorine, 
bromine, and nitrogen dioxide. 

HYDROGEN. 

Hydrogen rarely occurs in a free state under terrestrial 
conditions, though it has been found to a limited extent in 
certain volcanic emanations, in the gases given off by oil 
wells, and occluded in certain meteorites. 

The spectroscope has shown it to be present in the 
atmosphere of several of the heavenly bodies, especially the 
sun. 

Hydrogen was discovered by Cavendish in 1766 and 
called by him inflammable air; it was subsequently named 
hydrogen by Lavoisier. 



63 

Physical Properties. Hydrogen is a transparent gas, taste- 
less, colorless, and odorless. It is the lightest substance 
known. Water is 11160 times as heavy as hydrogen at G C. 
It is not poisonous though animals can not live in this gas 
alone, oxygen being necessary to life. Hydrogen being the 
lightest substance known it is conveniently taken as the 
standard for the specific gravity of gases — that is to say the 
standard to which other gases and vapors are referred. 

Owing to its great lightness hydrogen can be collected by 
downward displacement or poured upward from one vessel 
to another; on account of this property it is employed for 
filling balloons. 

Hydrogen is slightly soluble, water dissolving .02 of its 
volume at 0° C. and 30" barometric pressure. 

By great pressure and cold, hydrogen has been liquefied, 
giving^ a steel blue liquid. The conducting power of hydro- 
gen for heat is, according to Magnus, greater than that of 
any other gas. Another remarkable physical property is its 
great power of passing through animal and vegetable mem- 
branes and porous substances generally. This property is 
called diffusive power and it is a physical property common 
to all gases and vapors. The diffusive powers of gases are 
found to be inversely proportional to the square roots of the 
densities of the gases. Hydrogen accordingly diffuses far 
more rapidly than any other gas; because of this property 
hydrogen is more difficult to confine than any other gas. It 
will leak through a stop cock which will retain oxygen and 
nitrogen and it cannot be kept long in rubber bags, blad- 
ders, &c. 

The diffusive property of gases causes them to fill 
uniformly any space in which they may be placed. It also 
causes gases to mingle uniformly even against the force o\' 
gravity; thus if two vessels one containing oxygen the 
other hydrogen, be connected by a narrow tube with the 
oxygen below, in a short time they will be uniformly mixed. 



64 

The same result follows with any two gases that do not act 

chemically upon each other. 

The remarkable diffusive power of hydrogen may be shown by the 
following experiment — take an unglazed porous cup (a common bat- 
tery cup answers well) and close the open end with a cork through 
which extends a glass tube ; then invert this cup and insert the tube 
into a tightly sealed bottle arranged with a jet tube as shown in 
figure I. By placing a glass jar containing hydrogen over this cup the 
liquid may be forced out of the lower vessel in a jet several feet high. 
In this experiment the oxygen in the lower vessel passes out through 
the, porous pot into the hydrogen jar, but the hydrogen passes in much 
more rapidly and the pressure of the hydrogen added to that of the 
oxygen in the bottle drives out the water. The true diffusion of gases 
depends upon the motion of their molecules, but this diffusion is often 
complicated by the nature of the septa through which diffusion takes 
place. If the diaphragm exerts an adhesive or liquefying action on the 
gases, or if it is moistened with any liquid which exerts a solvent 
power on them, the simple diffusion passes into osmose or osmotic 
action. 

These processes are very important in nature; by true 
diffusion the uniform composition of the atmosphere is 
mainly maintained and the accumulation of noxious gases 
prevented, by osmose the function of respiration is per- 
formed and the aeration of the blood accomplished. Certain 
of the metals as platinum and palladium possess the power 
of absorbing and condensing within their pores large vol- 
umes of some of the gases. This action is called occlusion 
of gases. Certain meteorites have been found to contain a 
large amount of hydrogen indicating that they have come 
from regions where hydrogen exists at greater pressure than 
in our atmosphere. 

The terms osmose and diffusion are also applied to the 
processes by which substances dissolved in liquids pass into 
solutions of less density through diaphragms or against the 
force of gravity. 

Chemical Properties of Hydrogen. The chemical proper- 
ties of hydrogen cause it to combine readily with several of 
the non-metals but it shows little if any disposition to combine 



65 

with metals. The most evident chemical characteristic 
of hydrogen is its disposition to burn in oxygen. These 
gases may be mixed in any proportion and they will not act 
on each other at ordinary temperature, but if a jet of hydro- 
gen issuing into oxygen or air be touched with a flame it 
takes fire and burns producing great heat but very little 
light, the flame being barely visible. The result of the com- 
bination of hydrogen and oxygen is water as may readily be 
shown by holding a glass tube over the flame when moisture 
rapidly deposits on the side of the tube. 

Since hydrogen is inflammable and burns in the air it 
might be expected that it would not support the combustion 
of bodies which burn in oxygen. This may be proven by 
inserting a lighted taper into an inverted jar filled with 
hydrogen. The flame of the taper will be extinguished and 
the hydrogen will take fire and burn at the mouth of the jar. 

If a mixture of oxygen and hydrogen in certain propor- 
tion be raised to the temperature of ignition, which can be 
done by an electric spark or a flame, chemical union at once 
follows attended by violent explosion. This property of the 
gases makes great care necessary in experimenting with a 
mixture of them. 

Hydrogen weight for weight, produces more heat in burn- 
ing than any other substance. One pound of the gas in 
burning to water produces 34,462 units of heat. The explo- 
sion of the mixture of hydrogen and oxygen is of course due 
to the high temperature which results from the great heat of 
the chemical union, the heat expanding greatly the water 
vapor formed by the combination. The most violent explo- 
sion occurs when the gases are mixed in the proportion of 
two volumes of hydrogen to one of oxygen a fact shown by 
the formula of water. If air be used instead of oxygen the 
explosion will be less violent due to the presence of the inac- 
tive nitrogen. 

Owing to its tendency to combine with oxygen when 



66 

heated, hydrogen will take oxygen from many other bodies 
containing* it. This removal of oxygen is designated as a 
reducing or deoxidising process and the body accomplishing 
it is called a reducing or deoxidizing agent. Tims most of 
the metallic oxides are reduced at a red heat by hydrogen, 
which is one of the best reducing agents; for example 
CuO+H 2 =Cu+H 2 0. On the other hand a body which gives 
oxygen to another body is called an oxidizing agent. 

Preparation of Hydrogen. The process by which hydro- 
gen is usually prepared for laboratory purposes is to act 
upon dilute sulphuric acid with zinc. The zinc decomposes 
the acid with liberation of hydrogen and formation of zinc 
sulphate as indicated by the following reaction Zn+H 2 S0 4 = 
ZnSOd-H 2 . 

For this purpose the zinc is cut into small strips or 
granulated by pouring melted zinc into water from a 
moderate height ; a greater surface is thus exposed for con- 
tact with the acid. If the sulphuric acid is too strong the 
zinc sulphate formed does not readily dissolve off the zinc 
and the chemical action is retarded or stopped. On the 
other hand if the zinc be pure, it will scarcely act upon the 
acid; the action is generally facilitated by lead or other 
metal impurities which have an electrical effect not yet 
described. 

This method of preparing hydrogen can be followed in 
common Woullf bottles, shown at A in the figure. The zinc 
is put into the bottle and the acid added at B ; the hydrogen 
is passed out at the tube C and collected by displacement as 
described under oxygen. Hydrochloric acid may be used to 
replace the sulphuric in this process or iron may be used 
instead of the zinc, but the hydrogen from iron is generally 
less pme than that from zinc. 

Hydrogen may also be prepared by passing steam over 
iron turnings contained in a tube heated to redness. The 





!i 1 


11 




V 


Fia.3 
*WWf to £w*fc. 



67 

oxygen of the steam combines with the iron and the hydro- 
gen passes on through the tube — 3Fe+4H 2 0=Fe304+4H 2 . 

It will be observed that the physical properties of hydro- 
gen place it with the non-metals while the chemical proper- 
ties ally it to the metals. 

NITROGEN. 

Nitrogen occurs free in the atmosphere of which it 
constitutes about four-fifths, oxygen constituting nearly the 
whole of the remaining one-fifth. It also occurs in the 
volcanic gases, in the atmosphere of the sun, and in certain 
nebulge, and has been found in meteorites. In the com- 
bined form it exists as nitrous and nitric acids, in the 
compounds of ammonia, and in the organisms of plants and 
animals. 

Nitrogen was discovered by Rutherford of Edinburgh in 
1772. 

Physical Properties. Nitrogen is a colorless, transparent, 
odorless, and tasteless gas. Water at 60° F. dissolves less 
than .015 its volume. By great cold and pressure it has been 
liquefied and solidified. 

Chemical Properties. In its chemical deportment nitro- 
gen is very inert. It combines directly with only a few 
elements among which may be mentioned silicon, boron, 
magnesium, carbon, oxygen, and hydrogen; with the last 
named it combines when one or both elements are in the 
nascent state to form ammonia (NIL). 

It has no positive poisonous properties but is incapable 
of supporting respiration or combustion, oxygen being 
essential to these processes. 

Its presence in the atmosphere moderates the action of 
pure oxygen. 

The slight affinity existing between nitrogen and the 
other elements gives a characteristic property to its com- 
pounds many of which are very unstable; thus the nitro- 



68 

genized principles of plants and animals are prone to 
decomposition and many artificial compounds of nitrogen 
are highly explosive. 

Preparation of Nitrogen. Nitrogen is generally obtained 
in small quantity by burning phosphorus in air confined over 
water. A porcelain capsule containing phosphorus is floated 
on the water, the phosphorus is ignited and the whole 
covered with a bell jar. The burning phosphorus unites 
with the oxygen forming phosphoric oxide (P 2 5 ) which 
after a time is absorbed by the water. 

In larger quantity it may be prepared by passing air over 
finely divided copper heated to redness in a porcelain tube. 
The oxygen is removed by the copper. 

One of the easiest methods of preparing pure nitrogen is to heat in 
a glass retort potassium nitrite and ammonium chloride — KNCU+NH 4 
C1=KC1+2H 2 0+N 2 . 

ATMOSPHERIC AIR. 

The gaseous envelope surrounding the earth consists 
essentially of a mixture of nitrogen, oxygen and argon 
together with small but variable quantities of carbon diox- 
ide (C0 2 ), and water vapor with traces of other substances 
due to accidental or local causes ; among the latter may be 
mentioned ammonia (NH 3 ), marsh gas (CH 4 ), sulphuretted 
hydrogen (SH 2 , and sulphur dioxide (SO,), the last two may 
generally be detected near cities and towns. Argon has been 
only recently discovered and constitutes about one per cent, 
of the atmosphere. The thickness of the earth's envelope is 
estimated to be about forty-five miles measured from the 
earth's surface. The air probably extends beyond this height 
but is in an extremely rarefied condition. 

Physical Properties. The density of the air according to 
the law of Boyle rapidly diminishes with the height. Due to 
its weight the atmosphere exerts a pressure on all bodies. 
The assumed average pressure of the atmosphere at the sea 



69 

level has been generally adopted by engineers as the unit of 
pressure and this unit is named an atmosphere. The pres- 
sure is generally expressed in terms of the barometric col- 
umn, that is the height of the mercury column which the air 
will support. 

In British measure an atmosphere is equivalent to the 
pressure of 29.905 inches of the barometer at 32° F. at Lon- 
don and is very approximately 14.73 pounds on the square 
inch of surface. In the metric system the atmosphere is 
.00032 greater than in the British. 

For all ordinary chemical calculations it may be taken 
that water is 773 times as heavy as air, both taken at common 
standard temperature and pressure. 

Composition of the Atmosphere. We owe to Cavendish, 
1781, the first accurate determination of the proportions of 
the essential constituents of the atmosphere (N and O). 
These gases are mixed in the air very approximately in the 
proportion of 21% of oxygen and 79% of nitrogen by volume 
and 23% of oxygen and 77% of nitrogen by weight. There is 
but very little variation in the proportions of these constit- 
uents from whatever source the air is obtained. 

The proportion of the oxygen and the nitrogen can be 
very approximately found by passing air over very finely 
divided copper contained in a glass tube, carefully weighed, 
and heated to redness ; the nitrogen is made to pass into an 
exhausted globe. The increase in weight of the tube gives 
the weight of the oxygen and of the globe the nitrogen. 

The other two all pervading constituents of the air are 
water vapor and carbon dioxide; these vary with conditions. 

Carbon Dioxide of the Air. The amount of carbon diox- 
ide (C0 2 ) in the air varies slightly with the locality and with 
the season, being greater nearer centres of population than 
in the country and greater in winter than in summer. In the 
country a greater amount has been found in the air at nigh.1 



70 

than during the day, the difference being due to the different 
action of plants during the day and night; this diurnal varia- 
tion is not observed at sea. 

The amount of carbon dioxide in normal air is from three 
to four volumes in 10000. In cities, in winter and especially, 
in heavy fogs which prevent diffusion, it may rise to six or 
seven volumes in 10000. The amount of carbon dioxide 
though relatively very small is actually very great. 

Upon this gas the vegetable kingdom is dependent for its 
existence; plants by the aid of sunlight decompose the 
carbon dioxide retaining the carbon and returning the 
oxygen to the air. On the other hand all animal respiration 
and all ordinary combustion take oxygen from the air and 
return to it carbon dioxide. Owing to this cyclic process the 
change in the proportion of these constituents in the atmos- 
phere must be very slow. 

The quantity of aqueous vapor in the air is far less 
constant than the carbon dioxide. This quantity varies 
primarily with the temperature of the air as already ex- 
plained in the subject of heat. The other important circum- 
stances which affect the quantity are the prevailing direction 
of the winds, the configuration of the land, and the nearness 
of the bodies of water. Upon the average the aqueous vapor 
is from 1 to 1.5 volumes to 100 of air. 

Other Gaseous Constituents of the Air. Ozone can nearly always 
be detected in normal air and its presence is more common in the purer 
air. Hydrogen dioxide is also very generally present in the air and its 
chemical actions are in many cases analogous to those of ozone and it 
is difficult to distinguish between the two. Ammonia or more gener- 
ally its carbonate is nearly always present in minute but variable 
quantity in the air. The ammonia results from the decomposition of 
tlie organic matter and in the presence of moisture combines with the 
carbon dioxide and other acids present in the air; the nitrates and 
nitrites of ammonium are sometimes from this source present in the 
atmosphere. 

Other gases occur locally in minute quantities in the air, the most 
common of which have already been mentioned as sulphuretted 
hydrogen, sulphur dioxide, and marsh gas. 



71 

Solid Constituents of the Air. In addition to its gaseous 
constituents, minute particles of solid matter are suspended 
in the air and generally termed dust. Atmospheric dust is 
made up both of inorganic and organic matter. The in- 
organic matter is composed of various mineral compounds. 
The organisms are the propagators of mould, mildew, 
fermentation and putrefaction, and it is probable that the 
last named are the agencies through which certain diseases 
are spread. 

COMPOUNDS OF HYDROGEN AND OXYGEN. 

WATEE. 

Water is the most important compound of hydrogen and 
oxygen. With the exception of the air no substance is so 
indispensably necessary to terrestrial life as water. Its 
distribution is only second to that of the air and its absolute 
amount is enormously greater. Water is the cause of many 
of the most striking physical phenomena in nature and its 
uses for economical and domestic purposes are innumerable. 
Besides the enormous quantities which are spread over the 
surface of the earth and distributed as vapor through the air, 
it is an important constituent of all living beings and of 
many minerals. 

The composition of water was first discovered by 
Cavendish in 1781. 

Physical Properties of Water. Many of the physical 
properties of water are well known, a few will be men- 
tioned here. Thick layers of water have a blue color. 
Water has greatest density at 4° C. or 39.4° F. In freezing 
water expands by .09 of its volume so that eleven volumes of 
water become twelve volumes of ice. The melting point of 
ice under constant pressure is constant (0° C.=32 c F.) but 
water may be cooled below this point and still remain liquid. 

Water evaporates at all temperatures, and ice at tem- 
peratures below 0° C. will give oft' vapor without melting. 



7-2 

The absolute boiling point of water or the temperature above 
which it can not exist as a liquid is about 1076 c F. (580°C). 

As already stated water at maximum density is taken as the 
standard for the specific gravities of bodies in general and it 
is also the standard for the specific heats of bodies in gen- 
eral. One volume of water at the boiling point and under 
the standard pressure yields 1696 volumes of vapor at the 
same temperature and pressure, the specific gravity of the 
vapor being 0.622 (air = l). 

Solvent Power of Water. This power of water is not 
thoroughly understood. It may be defined as the power of 
water to form a homogeneous liquid with another substance 

brought into it. Thus many substances, gases, liquids, or 
solids brought into water disappear and a homogeneous 

liquid results. The results of these actions are such that the 
constituents can not be separated by purely mechanical 
means. The substance thus mingled with the liquid is said 
to be dissolved by it or in solution in the water. As already 

stated these solutions differ from mere mechanical mixtures 
and also to a certain extent from true chemical compounds. 
If a very small amount of the substance be dissolved in 
the water the solution is said to be dilute: when a large 
amount is dissolved it is a concentrated solution; and when 
the water will dissolve no more of the substance it is a satu- 
rated solution. There is no limit to the extent to which 
every solution may be diluted but in the case of gases and 
solids and of most liquids there is a limit to the amount of 
the substance that may lie brought into solution: but some 
liquids dissolve each other in all proportions, for example 
water and alcohol. 

Solution of Solids. The quantity of a solid required to 
produce saturation generally varies with the temperature, 
most solids being more soluble in hot than in cold water. If 
a saturated solution of such a substance be made in hot 



73 

water and then the water be allowed to cool it will, in general, 
not be able to hold so much of the solid in solution and the 
excess separates or as it is usually called is deposited in the 
solid form, often as crystals. 

The hot saturated solutions of some bodies do not deposit 
any of the dissolved substance if the solution is perfectly 
quiet while cooling and excluded from the air ; such solutions 
are called supersaturated. 

Water of Crystallization. Many salts in crystallizing from 
their aqueous solutions retain in combination a greater or 
less amount of water called water of crystallization for to it 
the form of the crystal is due. The amount of this water 
varies with the conditions of crystallization but the water 
and the salt are always present in molecular proportions by 
weight. Some salts when exposed to dry air lose their water 
of crystallization and crumble to a dry powder, this process 
is termed efflorescence. Those salts which do not part with 
their water of crystallization in dry air at ordinary tempera- 
ture, do so at the boiling temperature or at a somewhat 
higher one. 

Salts generally lose their color as well as their crystalline 
form by the removal of their water of crystallization. Some 
sympathetic inks owe their use to this property of changing 
color. A solution of the salt is used as ink but is invisible 
until the paper used for the writing is warmed ; cobalt chlo- 
ride is such an ink. 

Some salts retain a portion of their combined water 
usually one molecule more tenaciously than their water of 
crystallization; this is called ivater of constitution. In some 
cases it can be replaced by a salt. 

From the investigations of Guthrie it seems probable that all solu- 
ble salts form compounds with water at some temperature. Those 
Knits which combine with water and are soluble only at temperatures 
below 0° C are called crvo-h.vd rates. 

Many salts which solidify without combined water may 
enclose some water mechanically; such salts when heated are 



74 

likely to fly to pieces with a small report and are said 
to decrepitate. Bodies which absorb moisture from the air 
and become damp and ultimately liquid, are said to 
deliquesce. 

The thermal effect of the solution of a solid when there is 
no chemical effect is cold. 

Solution of Liquids. Water dissolves many liquids, some 
in all proportions. In such event it is usual to say that the 
liquids mix in all proportions, though the solution may be 
accompanied by a decided chemical action with a develop- 
ment of heat; water and sulphuric acid are examples. In 
other cases the solution is confined to certain limiting pro- 
portions of the liquids. In case of the solution of solids and 
liquids a contraction takes place in the volume of the solu- 
tion, the volume being less than the sum of the volumes of 
the two bodies. 

Solution of Gases. Gases are very generally soluble in 
water to a greater or less extent and the thermal effect of 
such solution is opposite to that in the case of solids, heat 
being produced. The heat is very evident when the gas is 
very soluble as in the case of ammonia and hydrochloric 
acid. Grases in most cases are removed from solution by 
heating, when not thus liberated they form definite com- 
pounds with the liquid and distil over with it; the compounds 
of hydrogen with the halogen elements are examples of this 
last class of gases. From the facts stated in regard to solu- 
tions it will be observed that, like alloys, they differ both 
from what we have defined as true chemical compounds and 
also from mere mechanical mixtures; perhaps the most 
evident distinction is that they differ from true chemical 
compounds by having no invariable composition, and from 
mechanical mixtures by the fact that, except in a few cases, 
there is a limit to the proportions in which the constituents 
may be present. 



75 

Chemical Properties of Water. It has already been 
stated that oxygen and hydrogen combining to form water 
develop great heat ; we should therefore expect water to be 
a permanent and stable compound. Although this is a fact, 
water can be readily decomposed in several ways. 

The alkali and alkaline earth metals decompose water at 
the ordinary temperature; for example, K 2 +H 2 0=K 2 0+H 2 . 

Some other metals do so at higher temperature. It may 
also be decomposed by the electric current. At high tem- 
perature water is decomposed into its elements, the decompo- 
sition according to Deville, beginning about 1000° C. and 
continuing with the increase of temperature up to about 
2500° C. when it is completed. After the decomposition has 
commenced any fall of temperature will cause a recombina- 
tion of the elements. 

This general decomposition of a substance with increas- 
ing temperature accompanied by a disposition of the con- 
stituents to combine and reproduce the substance by a 
reduction of temperature is called dissociation. 

In its action on vegetable colors, water is neither acid nor 
basic. It combines with both basic and acid oxides to form 
definite chemical compounds. Its combinations with the 
oxides of the alkali and alkaline earth metals develop much 
heat and result in the compounds called hydroxides; for 
example, K 2 0+H 2 0=2KOH, CaO+H 2 = Ca0 2 H 2 ; as already 
stated it is not believed that water as such exists in these 
compounds but the oxygen and the hydrogen are present in 
the form of hydroxyl. 

Water combines with the acid oxides to form acids; for 
example, H 2 0+S03=H 2 S0 4 . 

Composition of Water. The composition of water may 
be determined by analysis or by synthesis. The analysis or 
separation of water into its constituents, may be accom- 
plished by passing an electric current through it under 
proper conditions. With proper arrangements the con- 



76 

stituent gases may be collected and their volumes and 
weights determined. 

The composition by synthesis can be determined by 
causing oxygen and hydrogen to combine directly, as by the 
passage of the electric spark through a mixture of the gases 
under such conditions as give the volumes of the gases 
involved. From the volumes the weights can be computed 
from the relations of the specific gravities. 

The synthetic determination can be more accurately made 
by causing an unknown quantity of hydrogen to combine 
with a precisely determined weight of oxygen and then 
weighing the water produced. The difference between the 
weight of the water produced and the weight of oxygen 
employed gives the weight of hydrogen that has combined 
with the oxygen. This is designated as gravimetric syn- 
thesis and a convenient method often pursued is to pass pure 
dry hydrogen over a known weight of heated copper oxide 
and accurately weighing the water produced; the loss of 
weight in the copper oxide gives the weight of the oxygen ; 
the difference between this and the weight of the water 
produced gives the hydrogen; CuO-j-H2 = =H 2 + Cu. 

NATURAL WATERS. 

Pure water is seldom or never found in nature. The 
impurities result from the materials, solids, liquids, or 
gases with which it comes in contact and they may be either 
in suspension or in solution. Suspended impurities are 
merely finely divided particles of matter mechanically 
distributed in the water, and they may be gotten rid of by 
subsidence or filtration; water often contains no suspended 
matter. Soluble impurities must be separated by distillation 
or a combination of this with more purely chemical means. 

The natural waters may be classified according to their 
occurrence as rain, sea, river, spring and well waters. 

Rain Water. Rain is the purest form of natural water 
but even it contains gaseous and dust particles derived from 



77 

the atmosphere through which it passes. The gases dis- 
solved by falling rain are of course those present in the 
atmosphere. Rain water accordingly always contains 
oxygen and nitrogen and generally more or less ammonia 
and carbon dioxide and often traces of other gases the 
quantity depending upon local conditions. 

By boiling rain or other natural water the gases in 
solution are driven out and may be collected. It is thus 
found that the oxygen and nitrogen in solution in these 
waters are not in the same proportion as they exist in the 
air. This is one of the best proofs that air is a mixture of 
oxygen and nitrogen and not a chemical compound. 

Spring and Well Water. The rain and the water result- 
ing from the melting of snow, sleet, and hail flow over the 
surface of the earth on their way to the sea. When these 
waters sink below the surface and reappear, they constitute 
springs ; if their subterranean channels be tapped artificially 
we have wells. Spring and well waters, in addition to the 
impurities of rain water, dissolve many soluble substances 
encountered in their flow; the impurities in such water 
depending upon the rock material through which they pass. 

The most common and abundant impurities are the car- 
bonates and sulphates of the alkaline earth metals, the chlo- 
rides and sulphates of the alkali metals, silica (silicon oxide) , 
carbon dioxide, and hydrogen sulphide. 

Many other substances of less frequent occurrence and of 
less importance are found naturally in these waters. 

By contamination from artificial sources, as by city or town sew- 
age, etc., spring- and well, and even river waters may become very 
impure and entirely unfit for human consumption. It is believed thai 
zymotic diseases generally, and it is known that (wo i>\ them., cholera 
and typhoid fever, are frequently propagated by drinking-water. The 
infectious or zymotic matter is contained in the discharges of affected 
people and passes by defective drainage into sources of water supply. 
In cases of such artificial contamination the additional impurities in 
the water are salts of nitrons and nitric acids, ammonia, and chlorides. 
By chemical analysis and a consideration of the sources of a water 



78 

supply, its safety for drinking purposes can generally be determined, 
but any water contaminated by sewage should be classified as dan- 
gerous. 

Hard and Soft Water. Common waters have been roughly 
classified as hard and soft, a classification originally depend- 
ing upon their action upon soap. Soap when rubbed in soft 
water forms a lather much quicker than when hard water is 
used. With the latter white curdy flakes not observed with 
the soft water, make their appearance before a lather is 
formed; this action is due to chemical causes and will be 
presently explained. 

The hardness of water is mainly due to the presence in 
the water of the carbonates and sulphates of calcium and 
magnesium. The carbonates of the metals, except those of 
the alkalies, are not soluble in pure water but if the water 
contains carbon dioxide in solution, as natural waters 
generally do, they will dissolve the carbonates. 

Magnesium sulphate is readily soluble in water and cal- 
cium sulphate very slightly so. 

The hardness due to the carbonates in solution is termed 
temporary because it can be readily removed; that due to the 
sulphates is called permanent because of the difficulty of 
removing it. 

Since the temporary hardness brought about by the car- 
bonates in solution is due to the presence of carbon dioxide, 
if this be removed the carbonates will be precipitated. The 
carbon dioxide may be driven off by boiling, on account of 
its decreased solubility with increase of temperature, and 
the carbonates will deposit on the sides of the containing 
vessel. 

Calcium sulphate is very slightly soluble in cold water 
and less soluble at high temperature. By evaporation of the 
water and increase of temperature there would also be 
deposited some calcium sulphate, but the calcium sulphate 
can not be entirely removed by boiling alone. 



79 

These depositions explain the furring" of kettles and 
incrustations of boilers. These deposits are usually colored 
brown or red due to the presence of iron oxide and vegetable 
matter, the former resulting from the iron carbonate depos- 
ited from the water. 

The temporary hardness of the water may also be 
removed by adding to the water a solution of calcium hydrox- 
ide, which combines with the free carbon dioxide remov- 
ing it as calcium carbonate and causing the deposition of the 
dissolved carbonate, H 2 0+CaC0 3 +C0 2 +CaO a H 2 =2CaC0 3 + 
2H 2 ; this is the principle of the Clark process for softening 
water. 

Both the temporary and permanent hardness are removed 
by the household process of adding an alkaline carbonate to 
the waters, 

2Na 2 C03+H 2 0+CaC0 3 +C0 2 +CaS0 4 =Na 2 S0 4 +2NaHC0 3 

+2CaC0 3 , 

but this is practicable only on a small scale. 

It is often desirable to prevent the incrustation in boilers 
and the most efficient means yet suggested is to add 
ammonium chloride to the waters employed — there are then 
formed ammonium carbonate and calcium chloride, the 
latter remains in solution in the water and the former 
volatilizes in the steam, 

2NH 4 Cl+CaC0 3 =2(NH 4 ) 2 C0 3 +CaCl 2 . 

The incrustations formed in boilers fed with sea water 
are mainly due to calcium sulphate and magnesium chloride 
in sea water. 

Natural Deposits from Hard Water. The metallic car- 
bonates except those of the alkalies are insoluble or nearly 
so in pure water, but they dissolve in water containing 
carbon dioxide and the greater the amount of carbon dioxide 
the greater the amount of the carbonates dissolved. 

Subterranean waters are often heavily charged with 



80 

carbon dioxide and coming" in contact with limestone rocks 
they dissolve much calcium carbonate. When these waters 
come to the surface of the earth the carbon dioxide escapes, 
due to diminished pressure, and the dissolved carbonates are 
deposited. 

This explains the phenomena observed at the so-called 
petrifying' springs which are constantly depositing limestone, 
and will rapidly cover with it any body placed in their 
waters. This phenomenon is abundantly witnessed in the 
Yellowstone Park — the objects are merely coated and not 
petrified. 

Such waters trickling into caves often deposit their salts 
so as to form large columns, often of great beauty, called 
stalactites and stalagmites. 

Of course when waters containing salts in solution are 
evaporated, they then leave their salts behind, so that 
deposits may occur by evaporation of the water as well as 
by the removal of the carbon dioxide. 

It is possible that the solution of the carbonates generally by 
carbon dioxide in solution, may be due to the formation of acid 
carbonates of the metals, but the formation of these substances has 
not been proved and if they are formed they are easily decomposed, for 
as we have seen boiling" drives off the carbon dioxide; if this is the case 
the soluble carbonate of calcium is represented thus — 
CaC03+C0 2 +H 2 0=CaH 2 (C0 3 ) 2 . 

Action on Soap. To understand the action of hard water 
on soap it is necessary to know that soap is itself a metallic 
salt of an alkali metal and fatty acid and common soap may 
be represented by the formula NaFt in which Ft stands for 
the complex formula of the fatty acid radical. When these 
soaps are treated with hard waters the calcium and mag- 
nesium salts by double decomposition form the soaps of 
these metals which are insoluble and perceptible as curdy 
scum on the water. A true lather from the soap will not 
form until the salts to which the hardness is due are 
removed by the formation of these insoluble soaps. 



81 

River and Sea Waters. River water does not differ 
essentially from well and spring water. The quantity of 
both mineral and organic impurities being diminished by the 
conditions of continual motion and exposure to the air. 

Sea water contains the same salts as spring and river 
waters and in addition a large amount of common salt, about 
four-fifths of the saline constituents of sea water being 
sodium chloride. The compounds of bromine and iodine are 
also found in small quantities in sea water. A gallon of sea 
water usually contains about 2500 grains of mineral salts. 
Sea water has no point of maximum density above the freez- 
ing point and solidifies at — 2° C. 

Mineral Waters. Natural mineral waters are those spring 
waters which contain mineral substances in such quantity as 
to exert a medicinal effect on the animal system or as to ren- 
der them entirely unfit for drinking purposes. Mineral and 
medicinal springs are very widely distributed ; some of the 
common kinds are chalybeate springs, which contain some 
salt of iron in solution; saline springs which contain one or 
more of a large number of mineral salts ; carbonated springs 
which contain carbon dioxide in solution; hepatic springs 
which contain hydrogen sulphide in solution. The escape of 
the gaseous constituents often produce effervescence; the 
same spring often contains both solid and gaseous constit- 
uents. 

Purification of Water. Waters often become purer by 
natural processes. This is the case with running waters and 
especially when they are subjected to thorough agitation and 
exposure to the air; an unfit water may thus become fit for 
drinking in a purely natural manner. The purity of all turbid 
water is greatly increased by allowing it to stand in tanks or 
reservoirs, by which most of the suspended matter is depos- 
ited. After remaining for some time in storage reservoirs it 
is customary to filter all large water supplies. The most 



82 

common method adopted is to allow the water to flow through 
layers of sand of different degrees of coarseness. Sand 
filtration when properly carried on is very efficient in remov- 
ing all suspended impurities, but it has little influence on 
the dissolved matter. It is also claimed by Professors Koch 
and Frankland that sand filtration removes a very large per 
cent of microscopic organisms. Besides sand, filters of char- 
coal or of coke and sand have been employed for purification 
on a large scale. 

The Hyatt filter which is largely used in this country uses 
coke and sand, in this process a little alum is added to the 
water before filtration. 

Filters of finely divided iron have been used in Antwerp in case of 
very impure water ; these niters exert a chemical as well as a mechan- 
ical effect upon the water. There are many other methods of purifying 
drinking water on a small scale. For refined chemical purposes water 
is purified by distillation. 

Alum is frequently used to clarify water; the effect is probably 
mainly due to the fact that if there be any carbonates in solution in the 
water, the alumina is precipitated, which has a coagulating effect and 
carries suspended matter with it. 

HYDROGEN PEROXIDE — H 2 2 . 

This substance has the composition H 2 2 . It was discovered in 
1818. It is a great oxydizing agent in the case of many substances, 
readily giving up half its oxygen and being converted into water; 
upon other substances it acts as a reducing agent, being itself con- 
verted into water and oxygen liberated; it thus acts upon ozone — 
3 +H 2 2 =20 2 +H 2 0. 

Hydrogen peroxide is a colorless, transparent, syrupy liquid ; it is 
heavier than water, has a bitter taste, and mingles with water in all 
proportions. 

Its most useful applications in the arts are by virtue of its oxidiz- 
ing power. 

Paintings which have blackened due to the formation of lead sul- 
phide can be restored to their original color by washing with a dilute 
solution of hydrogen peroxide — the lead being converted into lead 
sulphate. It is very important to the student of chemical philosophy 
because of its chemical relations. 



83 

CARBON. 

Carbon occurs free in nature in three distinct allotropic 
forms — as diamond, graphite, and mineral coal. These 
three forms differ widely in appearance and physical proper- 
ties, but their chemical relations prove their identity. The 
first two are crystallized and very nearly pure carbon; the 
third is amorphous, uncrystallized and includes many vari- 
eties of coal differing greatly in purity — the three principal 
varieties are anthracite or hard coal, bituminous or soft coal, 
and lignite or brown coal. 

In combination carbon is widely distributed. It exists 
in combination with oxygen in the carbon dioxide of the air, 
is present in all mineral carbonates, and is a constituent of 
all organic substances. It is the element by virtue of which 
all organic substances turn black when heated with limited 
access of air. All forms of carbon are solid, insoluble in all 
ordinary solvents, fused iron being the only known solvent, 
non-volatile except at the high temperature of the electric 
arc. 

Diamond. This is one of the rarest of substances and one 
of the most precious gems. It is usually obtained from allu- 
vial washings and appears generally to have come from 
sandstone or quartzyte rock; nothing definite, however, is 
known as to its original formation. 

It crystallizes in forms derived from the octahedron and 
is the hardest substance known. For use in jewelry it is cut 
and polished so as to bring out the brilliancy of its faces. 
Besides its use in jewelry it is used for pointing drills for 
boring in hard rock, to cut glass, and its dust is used in 
polishing. 

If heated very highly out of contact with air, as by the 
electric arc, it is converted into a black mass resembling 
graphite, but without loss of weight. It can be burned in 
the air and then leaves a small quantity of ash. Recently 
diamond, or carbon crystallized with the lustre of diamond, 



84 

has been prepared artificially, but the crystals thus made 
were very small. 

Graphite. This is found in beds and veins in the oldest 
crystalline rocks, has a greyish black color and metallic 
lustre, and is so soft as to leave a mark when rubbed on 
paper. 

It is a very useful substance, being employed in making 
the so-called lead pencils, for covering iron to prevent rust, 
and for mixing with clay to make crucibles which are 
designed to stand high and sudden change of temperature. 
Graphite is often produced artificially in the cooling of 
molten cast iron. It is also used as a reducing agent in 
some metallurgic operations. 

AMORPHOUS CARBON. 

This term includes in addition to the native mineral coals 
all the common artificial forms of carbon. The mineral 
coals are fully described in mineralogy. The principal arti- 
ficial varieties of amorphous carbon are charcoal, lampblack, 
animal charcoal and coke. Lampblack is the form of car- 
bon which is often deposited upon cold objects by the flame 
of gas or burning oil. These combustible bodies are com- 
posed almost entirely of carbon and hydrogen, and if the 
flame could be cooled down or the supply of air limited, the 
carbon escapes combustion and is deposited in a finely 
divided state commonly called soot. 

Lamp-Black is manufactured by subjecting organic sub- 
stances rich in carbon to imperfect combustion; that is 
combustion with an insufficient supply of air. For this 
purpose oils, fats, resins, and tarry matters are burned with 
a limited supply of air and the products of combustion 
conducted through a flue into a large chamber, along the 
sides and from the ceiling of which are suspended large 
cloths upon which the unburned carbon is deposited. The 
lamp-black thus obtained usually contains resinous or oily 



,;.',,, , . 




^ fiat 4. 






85 

substances and other impurities depending* upon the organic 
body burned. It is however sufficiently pure for the pur- 
poses for which it is generally used; viz., printers' ink and 
black pigments. 

Charcoal. Charcoal is the form of carbon obtained by 
heating wood out of contact with air. If wood be heated in 
the air it is entirely consumed except a small quantity of ash 
which is composed of the incombustible mineral matter of 
the wood. The part that has disappeared, the sap and the 
woody fibre, are composed almost entirely of carbon, hydro- 
gen, and oxygen. The woody fibre (cellulose) which con- 
stitutes nearly the entire solid part of the wood is more than 
one half carbon the remainder being oxygen and hydrogen. 

If wood be heated to redness out of contact with the air, 
no combustion can occur, but under this temperature the 
constituent elements of the wood rearrange themselves into 
simpler and more stable compounds. In this change the 
carbon is mainly left, retaining the form of the wood, but 
largely diminished in volume and still more so in weight. 

This resolution of a complex substance into simpler and 
more stable forms under the influence of high temperature 
out of contact with air is termed destructive distillation. 

In the case of wood it is often called charring, coaling, 
or carbonizing. 

The earliest and still the most common way of preparing 
charcoal for fuel, is as follows: 

Preparation of Charcoal. Billets of wood are built into a 
mound or stock around an upright pole or bundle of brush- 
wood which is withdrawn after the stock is completed and 
leaves an opening called the chimney. The billets may be 
nearly vertical, or horizontal, or inclined at any angle. 
When completed the mound usually has a dome shape and 
may have a diameter varying from thirty to fifty feet and 
with a height from ten to fifteen feet. The finished heap is 



86 

covered with chips, leaves, soil and earth, and often the coal 
dnst of a previous burning" is used for this purpose. Numer- 
ous openings are left around the base of the mound for the 
admission of air and escape of the products of distillation. 

The kiln is kindled in the centre and after the fire is 
started the top is closed. More air is required in the early 
stages of the carbonization so that the openings at the 
bottom are gradually closed and the mound is left to 
smoulder and cool. By this process the weight of charcoal 
obtained never exceeds 25% of the wood used. In this 
country as in many other places kilns or charcoal ovens are 
often built of brick or masonry; they are generally rec- 
tangular with arched tops or of a bee-hive shape. In these 
ovens the destructive distillation is accomplished by the 
combustion of a certain portion of the wood of the heap. In 
this country there is claimed for such ovens an economy of 
time and a gain in the quantity and quality of the charcoal 
but these advantages are denied at other places — the ovens 
are sometimes arranged to collect the products of distillation. 

Charcoal is also made by the destructive distillation of 
the wood in cast iron retorts, the wood being placed in a 
perforated iron case within the retort. In this method the 
heat is obtained from other fuel than the wood itself, though 
sometimes the combustible products from the wood are led 
to and burned in the furnace beneath the retort. At other 
times these products are condensed and used in the prepara- 
tion of acetic acid, wood naphtha, and methyl-alcohol. 

Distillation in retorts yields a greater per cent of charcoal 
and of better quality than the methods first described. 

All forms of carbon thus obtained contain impurities due 
to the non-combustible and non-volatile mineral matter of 
the wood. 

Properties and Uses of Charcoal. The appearance of 
charcoal needs no mention. It is one of the most unchang- 
ing solids known under ordinary conditions. This property 



87 

of carbon has long* been recognized and is shown in the 
charring- of wood intended to withstand extended exposure. 
Oak staves planted in the bed of the Thames by the ancient 
Britons in their defensive works against Caesar were charred 
and thus have been perfectly preserved to the present day. 
Charred stakes for marking the limiting lines of estates are 
often used. 

Charcoal is very porous and due to this property exerts 
an absorbent action on many substances. Oxygen is ab- 
sorbed by it in considerable quantity and many other gases 
to a far greater degree. This is especially noticeable with 
those gases which can be readily liquefied. It absorbs under 
ordinary conditions fifty times its volume of hydrogen 
sulphide and twice that amount of ammonia. A gas thus 
absorbed if capable of oxidation will be acted upon by the 
oxygen also contained in the charcoal. This property of 
charcoal explains its frequent use in deodorizing offensive 
matter and in purifying offensive atmosphere. 

Ammonia and hydrogen sulphide are two of the most 
common products of putrefaction and both are readily 
absorbed by charcoal. 

The absorbing power of charcoal also extends to liquids 
and solids, it is accordingly used to make water filters. 

Water passed through a good charcoal filter is clear and 
odorless. It is especially efficient in removing coloring 
matter. The charcoal has to be periodically heated to 
retain its absorbent powers. 

Besides the above uses charcoal is largely employed as a 
fuel and in the manufacture of gun-powder. 

With a free supply of air it burns readily without flame, 
producing carbon dioxide and yielding about twice as much 
available heat as an equal weight of wood. One pound of 
carbon burned to carbon dioxide will produce 8080 units of 
heat, C. scale. Its use in the manufacture of gun-powder 
will be referred to under that subject. 



Animal Charcoal. This form of carbon is made by the 
destructive distillation of animal substances as bone, skin, 
blood, &c, commonly from the first named substance. 
Bones are composed approximately of one-third animal 
matter and two-thirds mineral matter, three-fourths of this 
mineral matter being calcium phosphate. The animal mat- 
ter is composed mainly of carbon, hydrogen, oxygen, and 
nitrogen. The result of the destructive distillation of bones 
is a charred mass consisting of about one-tenth carbon and 
nine-tenths mineral matter. 

The decolorizing power of this form of charcoal far ex- 
ceeds that of other forms and it has frequent technical 
application for this purpose and is used industrially in sugar 
refineries and distilleries. 

The products from the distillation of bones are often 
collected and used, and the mineral matter from the bone- 
black itself is eventually employed as a fertilizer. 

Coke. Common coke results from the destructive dis- 
tillation of soft or bituminous coal. This distillation is 
sometimes made by burning coal in heaps as in the conver- 
sion of wood into charcoal, but generally the coke is 
prepared in specially constructed ovens and of these there 
are many forms. They are constructed of suitable masonry 
lined with fire-brick. In some of these the heat for the 
distillation is obtained by burning part of the coal in the 
oven ; in others the heat is obtained without burning any of 
the coal in the oven. In the latter kind the combustible 
gases driven from the coke and other fuel are burned to 
supply heat. The forms of coke ovens are too numerous for 
description here, the object in all cases is to accomplish the 
distillation with as little consumption of fuel as possible. 

The ovens are also varied in construction, depending 
upon whether they are arranged to secure the tar and ammo- 
nia. In this country the coke is usually made in bee-hive 
ovens and the secondary products are not saved. In Europe 



89 

the retort-ovens are very generally employed, and, in certain 
localities, the by -products from the volatile constituents of 
the coal equal in value the coke produced. The coke con- 
tains in addition to the fixed carbon the incombustible ash of 
the coal. 

Coke is of a dark grey color with a slightly graphitic 
lustre ; it produces a much higher temperature than common 
coal and is much used in iron smelting and other metallurgic 
operations. 

Coke is always produced in the manufacture of coal gas, 
the coal in the operation being distilled in closed iron 
retorts. In this manipulation it often happens that some of 
the denser gases containing carbon and hydrogen driven 
from the coal are decomposed by the high temperature and 
the carbon deposited upon the sides of the retort and is 
known as gas-coke. It is used for plates in carbon batteries 
and also for the manufacture of carbon rods for electric arc 
lights. 

Chemical Properties of Carbon. Carbon at the ordinary 
temperature is an inactive element, not combining with any 
other element; at higher temperature it combines directly 
with sulphur, hydrogen, and oxygen and under proper con- 
ditions will combine with other elements; at elevated tem- 
perature it is especially active in combining with oxygen. 
Heated to redness it burns brilliantly in pure oxygen and by 
the aid of heat it abstracts oxygen from many oxides remov- 
ing and combining with the whole or a part of their oxygen. 

When burned with a full supply of air carbon always 
yields carbon dioxide ; with a limited supply, carbon monox- 
ide is produced. In case an oxide gives up its oxygen at a 
low temperature to carbon, carbon dioxide is formed, but if 
a high temperature is required carbon monoxide is produced; 
these actions are represented by the accompanying *e- 
^tien^ 2CuO+C=2Cu+C0 2 ; 2ZnO+2C=2Zn+2CO. 



90 

This removal of oxygen from a body has already been de- 
fined as a reduction, hence carbon is a reducing agent. It is 
the most important reducing agent employed in the indus- 
trial arts and upon this property and its heat giving power 
depend its uses in metallurgic operations. 

COMPOUNDS OF CARBON AND OXYGEN. 

CAEBON DIOXIDE. 

There are known two compounds of carbon and oxygen, 
carbon monoxide and carbon dioxide, both of which are 
gaseous at ordinary temperature. The latter is the more 
important; it has already been stated that it is a constitu- 
ent of the atmosphere, being normally present in the propor- 
tion of from three to four volumes in 10000 of the air. Its 
constant occurrence in the air is readily understood from 
known considerations. 

It is the product of the combustion of any form of carbon 
or any compound of carbon in a full supply of air. As all 
common fuels are composed mainly of carbon or its com- 
pounds it may be said that carbon dioxide is an abundant 
product of all ordinary combustion. 

It is likewise, given on 2 in all animal respiration, the 
oxygen of the air which is inspired combining with the 
carbon of the system to form carbon dioxide which is 
exhaled. 

All living vegetation extracts carbon dioxide from the air, 
but when the plant dies the process of decomposition in the 
course of time restores the carbon dioxide to the air again. 
If the plant is devoured by animals or consumed for fuel its 
carbon eventually returns to the air as carbon dioxide. 

Carbon dioxide is also given off to the air during the 
processes of fermentation and putrefaction of organic sub- 
stances. 

It is present to a greater or less extent in all spring 
waters and in some places, especially in volcanic regions it 



91 

escapes rapidly from such waters when they come to the 
surface, giving effervescing springs. It often issues in 
considerable quantity from openings in the earth's crust. 
When coming from such openings or even from springs it 
sometimes accumulates in neighboring depressions in such 
quantity as to destroy the life of animals venturing into 
them. Such a poison depression has been found at the east 
side of the Yellowstone Park ; the poison valley of Java is 
another and the accumulation of gas around the soda springs 
(so called) in south eastern Idaho often causes the death of 
birds seeking water. 

The air which permeates soils is found to be richer in 
carbon dioxide than is atmospheric air. 

In the combined form carbon dioxide occurs as a con- 
stituent of all limestones and other carbonates and conse- 
quently exists in this form in enormous quantity. It 
constitutes over 96 per cent of oyster shells and egg shells. 

Physical Properties of Carbon Dioxide. Carbon dioxide 
at ordinary temperature is a colorless gas, and has a slightly 
acid taste and smell. Its formula shows it to be much 
heavier than air and its greater density explains its disposi- 
tion to seek the lower levels. At 14° C. water dissolves its 
own volume of carbon dioxide and the quantity dissolved is 
directly proportional to the pressure to which the gas is 
subjected. When the pressure is diminished or removed 
the amount dissolved is diminished and if there is much 
diminution of pressure the gas escapes with effervescence. 

Carbon dioxide can be liquefied without very great difficulty to a 
mobile colorless liquid which will not mix with water. Its boiling- 
point in the liquid state is —88° C. (much of the liquid carbon dioxide is 
now manufactured for use as a fire-extinguisher). By causing it to 
evaporate under an air pump its temperature is lowered to — 130° C. 
Like many other bodies which are liquefied only by very great pressure 
its coefficient of expansion is very great, being greater than the 
coefficient for gases. 



92 

Chemical Properties of Carbon Dioxide. Carbon dioxide 
is not combustible as it can not take up more oxygen. It 
will not support ordinary combustion and will extinguish 
flame ; a few bodies which have a great affinity for oxygen 
will burn in carbon dioxide. If potassium be ignited and 
then dipped into a jar of carbon dioxide it will continue to 
burn. Air which contains less than 3 per cent by volume of 
carbon dioxide will extinguish a taper — that is when the 
carbon dioxide is about one-eighth the volume of the 
oxygen. Carbon dioxide is not poisonous when taken into 
the stomach but it will not support respiration. It is not 
poisonous in this case, but merely suffocates by depriving of 
the necessary amount of oxygen and also prevents the 
escape of the carbon dioxide from the system. 

A taper burning in a confined space is extinguished as 
soon as the carbon dioxide reaches a certain amount and 
long before all the oxygen is exhausted. Similarly confined 
air becomes unfit to breathe long before the oxygen is 
exhausted. Any considerable amount of carbon dioxide 
above the normal in air to be respired is objectionable in 
that it diminishes the proportion of oxygen. The actual 
amount of pure carbon dioxide that must be present in the 
air to render it unfit for respiration is not definitely settled. 
It has been found that air containing as much as 5 per cent 
may be breathed without injury and recent experiments indi- 
cate that a much larger proportion of pure carbon dioxide 
may be breathed for several hours without ill effect. 

It has been shown that the bad effects experienced in 
poorly ventilated rooms are due to other waste products, 
than carbon dioxide, given off from the lungs during respira- 
tion. Besides the carbon dioxide, water vapor, nitrogen, 
and oxygen of the expired air, there are other organic sub- 
stances undergoing decomposition which have a poisonous 
action in the system and to these are to be largely attrib- 
uted the unwholesome conditions so rapidly developed in 



93 

overcrowded and poorly ventilated rooms. As carbon diox- 
ide is constantly given off in respiration along with other 
organic impurities the amonnt of the first in the air will 
indicate approximately the quantity of the latter and there- 
fore may be taken as a test of the fitness of the air for res- 
piration. 

Generally speaking it may be stated that when the 
volume of the carbon dioxide is over oVo the volume of the 
air it should not be breathed for any considerable time; 
when the volume of the carbon dioxide reaches 2017 the 
volume of the air, its effects soon become perceptible in lan- 
guor and disagreeable sensations and any amount above this 
is very deleterious ; when the amount has reached three per 
cent it has been known to produce death. 

A well, fermenting tun, or any confined space where this 
gas is suspected, should be tested before entering it. If a 
candle flame is made dim by the air the space should be con- 
sidered unsafe. When any person is quickly overcome by 
such an atmosphere another person can not safely go to the 
rescue without first increasing the proportion of oxygen to 
the carbon dioxide. This may often be quickly done by 
moving an open umbrella, a bundle of straw or of brush up 
and down through the space. 

The above described properties of carbon dioxide make 
evident the necessity for good ventilation. The amount of 
carbon dioxide given off from the lungs and skin amounts 
to about ro cubic feet per hour, an ordinary three-foot gas 
burner gives off about two and one-half times that amount. 
In order that the added carbon dioxide shall be distributed 
through the proper amount of air to fit it for respiration, 
it is evident that a large amount of fresh air must be intro- 
duced into constantly occupied rooms. It is of course easy 
to compute this amount under any given conditions. In 
general it may be stated that perfect ventilation should be 
prepared to supply one thousand cubic feet of air per man 



94 

per hour, though one half that amount is usually considered 
good ventilation. 

Preparation of Carbon Dioxide. Carbon dioxide is in- 
variably produced when carbon is burned in a full supply of 
oxygen; for example, C+0 2 =C0 2 ; from this source it always 
contains other substances. 

It is readily prepared for laboratory purposes by acting 
upon fragments of marble (CaC0 3 ) with dilute hydrochloric 
acid. The carbon dioxide escapes with effervescence and is 
usually collected by downward displacement as it is some- 
what soluble, in water. The apparatus described for making 
hydrogen may be used in this case. The action is repre- 
sented thus, CaC0 3 +2HCl=CaCl 2 +H 2 0-fC0 2 . 

Any of the other mineral acids will liberate carbon 
dioxide from a carbonate, so that it can be readily prepared 
in many ways. 

Carbon dioxide is largely used in the manufacture of 
artificial mineral waters. 

Carbonic Acid and Its Salts. An aqueous solution of 
carbon dioxide exhibits weak acid properties. It colors blue 
litmus red, but the blue color returns upon drying. The 
solution acts upon bases and forms the salts called car- 
bonates. The formulae of the carbonates indicate the ex- 
istence of an acid having the formula H 2 C0 3 though this 
substance has not been isolated. It is probable that the acid 
is formed whenever carbon dioxide is passed into aqueous 
solution, but it readily breaks up into carbon dioxide and 
water. On account of the similarity of the carbonates to 
other salts, they are universally considered as formed by the 
replacement of hydrogen in carbonic acid by metals and the 
acid is bibasic. 

The carbonates are a very important class of bodies and 
it may be well to repeat their properties. The carbonates 
are all decomposed by mineral acids, are all, with un- 



95 

important exceptions, insoluble in water except the car- 
bonates of the alkalies, and are all decomposed by heat 
except those of the alkalies. They are all soluble in water 
containing' carbon dioxide. 

CARBON MONOXIDE. 

Physical Properties. Carbon monoxide is a colorless, 
tasteless gas with a very faint smell; it is slightly lighter 
than air as may be seen from its formula. It is almost 
insoluble in water. Its critical temperature is about — 140° C. 

Chemical Properties. Carbon monoxide is an extremely 
poisonous gas. It acts upon the red corpuscles of the blood 
and deprives the blood of its power of distributing oxygen to 
the system. It forms am explosive mixture with one half its 
volume of oxygen. It burns in air with a pale blue flame 
producing carbon dioxide, but extinguishes ordinary flame. 
At high temperature it readily takes oxygen and forms 
carbon dioxide; for this reason it is a powerful reducing 
agent removing oxygen from many metallic oxides and 
reducing them to the metallic state. It is accordingly a very 
valuable agent in many metallurgic operations. Its union 
with oxygen gives out much heat; carbon monoxide burning 
to carbon dioxide gives more than two-thirds of all the heat 
produced by the complete combustion of the carbon to 
carbon dioxide. 

Production and Uses. Carbon monoxide is always pro- 
duced by the incomplete combustion of carbon or carbon- 
aceous substances, that is when these are burned with an 
incomplete supply of air. 

If carbon dioxide be passed over heated charcoal or other 
carbon it gives up one half its oxygen to the carbon, both 
being converted into carbon monoxide, as indicated by the 
reaction C0 2 +C=2CO. 

This action explains the phenomenon frequently observed 
in connection with an open anthracite coal fire when a pale 



96 

blue flame is seen to play over the top of the mass of coal ; 
the combustion of the coal in the lower part of the grate 
with full supply of oxygen produces carbon dioxide, this 
passing through the heated layers of coal above, is converted 
into carbon monoxide. This carbon monoxide upon reach- 
ing the upper surface of the coal comes in contact with the 
air and burns with the blue flame observed. 

This ready production of carbon monoxide is often made 
use of in metallurgic operations when it is desired to have a 
flame play over the surface of an ore placed on the hearth of 
a reverberatory furnace. 

Anthracite coal which burns with but little flame is 
frequently employed in such furnaces and it then becomes 
necessary to heap the coal in the grate so as to form a mass 
of considerable height. The carbon monoxide is produced 
precisely as described above in the grate and passes into the 
furnace chamber and when air is admitted the carbon 
monoxide burns with a flame. By properly regulating the 
supply of air a high temperature can be produced. 

The attraction which carbon monoxide has for oxygen at 
a high temperature enables it to remove this element from 
many of its compounds. Carbon monoxide is accordingly 
one of the most powerful reducing agents and, as will be 
subsequently seen, the property is generally turned to 
account in removing oxygen from the metallic oxides, 
reducing the oxides of the metals. 

Carbon monoxide is one of the essential elements of water- 
gas, hydrogen being the other; carbon dioxide and nitrogen 
are also present in limited quantities. This water gas is now 
largely used for illuminating and for other purposes. 

Water gas is prepared by passing steam over white-hot 
coke, the result is indicated by the reaction C+H 2 0=CO-f H 2 . 

Some carbon dioxide is also present for the reason that at 
lower temperature the action of steam on carbon is to pro- 
duce carbon dioxide ; at certain temperature steam also acts 



97 

slightly on carbon monoxide producing carbon dioxide. 
Water gas usually consists of about 30% of hydrogen and 
40% of carbon monoxide the remainder being nitrogen and 
carbon dioxide. 

As both hydrogen and carbon monoxide burn with faintly 
luminous flames, the gas to be used as an illuminant must 
be enriched or carburetted. This is accomplished by ad- 
mitting naphtha or crude oil to the heated coke during the 
gas production or by passing the gas through naphtha or over 
liquefied naphthalene. 

Water gas is valuable as a heat producer and then does 

not need to be carburetted. Its flame is entirely free from 

smoke and comparatively so from sulphur compounds. It 

produces a high temperature and a clear heat and is very 

valuable in melting and welding metals and in porcelain and 

glass manufacture. 

For laboratory purposes carbon monoxide is readily obtained by 
heating* potassium ferrocyanide with dilute sulphuric acid. 

COMPOUNDS OF CAEBON AND HYDKOGEN. 

Carbon and hydrogen form a larger number of com- 
pounds than any other two elements. These compounds ar,e 
designated as hydrocarbons. They enter largely into the 
composition of nearly all combustible bodies and include 
many of the inflammable gases, naphtha, benzene, &c. 

It is probable that all hydrocarbons are primarily derived 
from the organic kingdom and the study of these compounds 
belongs to organic chemistry. Only three of the simple 
hydrocarbons will be mentioned here; they are all con- 
stituents of common coal gas. 

methane; marsh gas; ch 4 . 

Methane is the only hydrocarbon containing one atom of 
carbon. It is found abundantly in the free state in nature. 
It is frequently termed marsh gas from its occurrence in 
marshy places. The bubbles of gas which rise to the surface 



when the mud at the bottom of stagnant pools is disturbed, 
are in fact marsh gas. It is believed to be one of the 
products of the decomposition of vegetable matter during 
its conversion into coal, hence its frequent occurrence in 
coal mines, where it is known as fire-damp. It is probable 
that all the hydrocarbons of petroleum and similar oils 
generally are derived in the same way. 

Physical and Chemical Properties. Methane is a color- 
less, odorless, and tasteless gas. Its formula shows it to be 
much lighter than air, hence it diffuses and mixes rapidly 
with it. When mixed with oxygen or air in suitable pro- 
portions it explodes violently upon ignition. The most 
violent explosion is indicated by the reaction, CH 4 +04= 
C0 2 +2H 2 0, in which there is just enough oxygen to com- 
pletely oxidize the carbon and hydrogen. The relative 
volumes of marsh gas and oxygen for this action are shown 
in the equation to be two volumes of oxygen to one of marsh 
gas ; it would accordingly require ten volumes of air for the 
complete oxidation of one volume of marsh gas. 

It is marsh gas which so frequently gives rise to the fatal 
explosions in coal mines. It will be observed that the pro- 
ducts of the explosion are also irrespirable and constitute 
the after-damp of mine explosions. 

Marsh gas has not been prepared by the direct union of 
its elements but can be prepared artificially. Marsh gas 
does not unite with other bodies without decomposition; 
chlorine decomposes it in direct sunlight, atoms of chlorine 
successively replacing atoms of hydrogen. At a high tem- 
perature marsh gas is separated into carbon and hydrogen. 

acetylene; ethene; c 2 h 2 . 

Acetylene can be produced directly from its elements by 
highly heating carbon in an atmosphere of hydrogen. This 
may be accomplished by immersing the electrodes of a 
voltaic arc in an atmosphere of hydrogen. The operation 



99 

is of but little practical importance but it is of great theo- 
retical interest because it is the first step in the artificial 
production of a large number of organic compounds. 

Physical and Chemical Properties. Acetylene is a color- 
less gas having a faint odor of geranium. From an ordinary 
gas jet it burns with a smoky flame, but when the air and 
gas are properly apportioned its flame is brilliantly luminous. 
It inflames spontaneously when brought into contact with 
chlorine and when mingled with air gives a mixture that can 
be exploded by ignition. 

Preparation of Acetylene. Acetylene is now prepared on 
a large scale by heating lime with powdered coal or other 
carbon in an electric furnace, by which calcium carbide is 
prepared. The calcium carbide if immersed in water yields 
lime and acetylene by this reaction, CaC 2 +H 2 0=CaO+C 2 H 2 . 

This method of preparing acetylene promises to give it a 
brilliant future as an illuminant for which purpose it is 
admirably adapted because of its great light giving power in 
proportion to the heat and objectionable products resulting 
from combustion. 

OLEFIANT GAS; ETHYLENE; C 2 H 4 . 

Olefiant gas like the other two hydrocarbons just de- 
scribed is a product of the destructive distillation of coal. 
It may be obtained artificially by the action of sulphuric acid 
upon alcohol. It is a colorless gas with a somewhat ethereal 
odor. It burns with a luminous flame and for complete 
combustion one volume of the gas requires three volumes of 
oxygen, C 3 H 4 +0«=2CO s +2H 2 0. 

The mixture of olefiant gas and oxygen in this proportion 
explodes with violence when ignited. 

The gas unites with chlorine and bromine, forming oily 
liquids, hence the term olefiant (oil-making). This action 
may be applied to determine the amount of the ethylene in 
the coal gas. 



100 

When subjected to high temperature olefiant gas is 
decomposed with a deposit of carbon and a separation of 
hydrogen, mash gas, and acetylene. 

CUMBUSTION AND FLAME. 

Combustion. The hydrocarbons above described, either 
separately or together, are found in many of our common 
inflammable gases; combustion and the properties of flame 
are accordingly very naturally taken up here. 

Combustion in general may be defined as chemical action 
accompanied by heat and light. The term combustion ordi- 
narily applies to the chemical combination of the oxygen of 
the air with the body burned. 

The temperature to which a body must be raised in order 
that combustion may take place is called the igniting point. 

When a body is said to be combustible it is generally 
meant that it burns in air. It is also customary to regard 
one of the bodies taking part in the action as the combusti- 
ble and the other as the supporter of the combustion. The 
enveloping medium is usually taken as the supporter of 
combustion and the other as the combustible, so that in the 
ordinary cases air is the supporter of combustion. These 
limitations are without scientific basis and the supporter of 
combustion may be any medium in which the phenomenon 
will occur. 

The process with proper arrangements, when both the 
bodies taking part in the combustion are gases, is reversible 
so that the supporter of combustion may become the com- 
bustible and the reverse; — thus while we usually burn hydro- 
gen in oxygen, oxygen may be burned in hydrogen. 
Similarly air may be burned in coal gas and the reverse. 

Flame. When both substances taking part in the com- 
bustion are gases, the action results in flame, which may be 
defined as gaseous matter heated to a temperature at which 
it becomes visible. Solids which do not volatilize at the tern- 



101 

perature of combustion do not give flame; carbon and iron 
are familiar examples. 

Luminosity of Flame. This may be due either to the in- 
candescence of gaseous matter or of solid particles present 
in the flame. A high temperature is always essential to in- 
candescence and consequently to luminosity. In all ordi- 
nary flames the gaseous matter which is heated results from 
the flame-gases themselves; the solid matter may result 
from these gases or may consist of foreign matter introduced 
for the purpose. 

It has been found as a general rule that denser gases and 
vapors when heated give off light at lower temperature than 
the less dense, and heated solids emit light at lower temper- 
atures than gases. 

Luminosity without Solid Particles. Examples of com- 
bustible bodies which afford dense flames and bright light 
without solid particles are seen in the case of phosphorus, 
arsenic, and carbon disulphide, which when burned in oxy- 
gen produce highly luminous flames, though all the products 
of combustion are gases at the temperature. The luminosity 
of the flame does not depend entirely upon the vapor density 
of the constituent gases themselves, but are affected by the 
pressure to which these gases are subjected. 

The luminosity of flame may often be increased by in- 
creasing the pressure of the medium surrounding the flame. 

Thus the luminosity of the flame of carbon monoxide 
burning in oxygen at ordinary pressure is only moderately 
luminous, but may be greatly increased by doubling the 
pressure. The faintly luminous flame of hydrogen burning 
in oxygen may be greatly brightened by increasing the pres- 
sure of the oxygen. For this reason a candle burns more 
brightly at a low than a high elevation. 

Flame Containing Solid Matter. The light-giving power 
of many of the common illuminating gases is still further 



102 

increased by the presence of solid matter intentionally intro- 
duced into the flame or separated from the flame-gases 
during' the chemical action of combustion. The Welsbach 
burner, among common gas-burners, is an illustration of free 
foreign solid matter introduced into the flame. The great 
luminosity in this burner is due to the introduction into the 
flame of a gauze hood of certain infusible metallic oxides. 

In the candle, oil lamp, simple gas-flames, and common 
flames generally, the light is mainly produced by the incan- 
descence of solid carbon particles which are separated in a 
finely divided state from the flame-gases. There are also 
usually present or produced in these flames dense hydro- 
carbons which emit light. The influence of such solid parti- 
cles may be illustrated by blowing powdered charcoal across 
a hydrogen flame. 

The calcium or lime-light owes its luminosity to a frag- 
ment of lime very highly heated by the oxyhydrogen 
flame. 

It is seen from the above considerations that the most 
essential conditions for luminosity in a flame are — (1) high 
temperature and vapors which are of themselves dense or 
made dense under the conditions of burning, (2) highly 
heated solid particles; the influences of these conditions 
operate simultaneously in most common illuminating flames. 

Structure of Flame. The simple flame is one that results 
from the combustion of a substance that undergoes no decom- 
position, but combines directly with the supporter of the 
combustion — hydrogen and carbon monoxide burning in 
oxygen are illustrations. There is but a single product of 
combustion in such cases. All such flames when the gas 
issues from a circular jet consist of a conical sheath of flame 
surrounding a cone of the gas. The flame-cone is hollow, 
that is to say, the interior cone of the gas is not burning. 
This fact may be simply proved by quickly depressing a 
white sheet of paper into the flame, when the flame cone will 



103 

char an annular space while the interior circle will be 
unaffected. A live match may be suspended in the inner 
cone without ignition if not allowed to touch the sides of the 
flame-cone. The conical shape of the flame is due to the 
fact of the gas issuing from the jet in the form of a cylinder, 
and being under a little greater pressure than the air, 
assumes the form of a slightly diverging cone. 

The gas first issuing from the jet burns as a ring around 
the orifice, the next layer of gas must pass above this ring in 
order to reach the air for its combustion. Each successive 
ring must pass through the preceding to reach the air and as 
each burning ring diminishes the volume of unburned gas 
these rings must grow smaller and the converging cone is 
the only possible form. This explanation holds for the 
shape of the candle flame or other flame resulting from the 
issuance of gas from a cylindrical wick. 

Hydrocarbon Flames. It has already been stated that 
these bodies enter largely into the composition of all our com- 
mon illuminating oils and gases. These bodies undergo 
decomposition during the combustion and the products of 
combustion are produced at successive stages. They give 
rise to flames more complex in structure than those just 
described. The common flames under this head are those of 
gas, oil, and the candle, the last will be described as typical 
of all. 

In the first case the fuel is supplied at the burner in the 
gaseous state, the gas having been obtained from the 
destructive distillation of coal at a distance; in the sec- 
ond (oil) the fuel is liquid and is converted into gas at the 
lamp. In the candle the tallow or wax is solid, so that it 
must be melted and distilled during the operation of burning. 

Candle Flame. In the candle flame there are three eon- 
centric cones; the interior is dark and is composed of 
unburned gas resulting from the destructive distillation of 



104 

the tallow, the next and the largest part of the name, is 
brightly lnminons and the outer cone is thin and only faintly 
luminous. There is also a bright blue cup at the base of the 
cone. 

The flame-cone proper consists of the outside and faintly 
luminous cone, the next or luminous one, and the blue cup at 
the base; the interior dark cone consists of combustible 
gases to which air does not penetrate and is not part of the 
flame. In the luminous cone combustion is taking place, but 
the air supply is not sufficient for complete combustion. At 
the temperature of the cone there results a decomposition of 
some of the hydrocarbons with a separation of free carbon. 
This free carbon heated to whiteness by the burning hydro- 
gen and other gases confers the great luminosity upon this 
cone. In the outer cone where the air supply is sufficient, 
more complete combustion takes place with production of 
great heat but little light. 

The blue cup at the base is due to the perfect combustion 
of a thin layer of gas 'at that point and to the lower temper- 
ature due to the presence of an excess of air. 

The combustible gases of the inner cone may be readily 
extracted and burned at some distance from the flame by 
inserting one end of an open glass tube six or more inches 
long into the cone. 

The unburned carbon in the luminous cone can be shown 
by depressing upon it a white porcelain plate. 

Flame for Special Purposes. Lighting Flames. From 
the foregoing considerations of the nature, properties, and 
structure of flames, it is evident that several considerations 
must enter into the construction of burners for different 
purposes. The Argand gas-burner is one of the most widely 
used burners for gas-lighting. The gas in this burner issues 
from the annular space between two concentric cylinders; 
the gas-flame is a hollow cylinder which is surrounded by the 
chimney and air is supplied to the flame both from the inside 



105 

and outside of the cylinder. The chimney acts effectively 
both in producing a draught and thus giving a liberal supply of 
air, which in combination with the regulated flow of gas per- 
mits the proper adjustment of the two for the best light. If 
there be too great a proportion of the gas some of the carbon 
escapes unburned and the flame smokes and the temperature 
is not high enough to produce a brilliant light. By using two 
chimneys and causing the air that feeds the flame to pass 
down between them, there is less chilling effect on the flame 
and an equal light may be obtained with a less consumption 
of gas. The Argand burner may be converted into the Wels- 
bach, already referred to, by the insertion of a durable gauze 
cylinder into the flame and regulating the air and gas sup- 
plies so as to produce the highest temperature. 

Smokeless Flames. Since luminous flames in general 
contain unburned carbon, they deposit soot when the flames 
come in contact with solids. When bodies are to be heated 
by flame as in laboratories and in kitchens, it is therefore 
advantageous to have flames in which the combustion is 
as perfect as possible, producing a smokeless flame. 

Smokeless Flames. This result is accomplished by mix- 
ing the air and gas in certain proportions before combustion, 
so that the hydrocarbons are burned without the separation 
of carbon, this also causes the disappearance of the 
luminous part of the flame. By a proper adjustment of the 
air and gas the flame from the combustion of a given amount 
of gas is smaller and the temperature higher. 

The principle upon which smokeless burners are con- 
structed, is well shown in the Bunsen burner. This burner 
in its simplest form, consists of a cylindrical tube mounted 
on a substantial base. The gas is led in at the base and 
ascends the tube, near the bottom of which there are two 
holes for the admission of air. The flow of the gas draws air 
into the tube and the mixture is burned at the top of the 
tube. The holes for the admission of the air can be entirely 



106 

or partly closed. By entirely closing the air-holes the flanie 
is white and lnminons, by admitting the proper proportion 
of air the flame becomes smaller, of a bine color, and almost 
non-lnminons. This loss of color was formerly supposed to 
be almost entirely due to the complete combustion of the 
hydrocarbons without the separation of the carbon. It is 
now known that the effect can be brought about by admix- 
ture with the hydrocarbons of other gases than air, as 
nitrogen and carbon dioxide. The loss of luminosity in the 
case of air is due partly to the more perfect combustion, to 
the cooling effect of the nitrogen, and to the fact that in the 
presence of nitrogen a higher temperature is required to 
decompose the hydrocarbons. The cooling effect of the 
nitrogen prevents the separation of the carbon at certain 
parts of the flame, but the more perfect combustion makes 
the temperature at other parts higher than the corresponding 
parts of the luminous flame. 

The flame of the ordinary Bunsen burner consists of only 
two cones. The inner cone is a mixture of air and gas; 
combustion is taking place only in the outer one. That the 
flame does not travel inward is due to the rate of motion of 
the mixed gases ; in the outer cone this speed is diminished 
so that the gases can be raised to the point of ignition. If 
the rate of flow of the gases be diminished the flame will 
penetrate further and further inward and can be made to 
strike down the tube to the point of inflow of the gas and air. 
The absence of flame in the inner cone of the Bunsen burner 
may be shown in the manner already given for common 
flames. 

The Blow-pipe Flame. This flame is produced by forcing 
a stream of air across a common gas, candle, or lamp-flame. 
The mouth blow-pipe is an instrument of great utility. In 
its simplest form it consists of a bent tube terminating in a 
small end with an aperture. This flame shows three cones 
but they are peculiar in appearance being long and pointed. 




G.8. 



107 

The innermost cone is composed of a mixture of air and 
combustible gases not in the state of combustion ; the second 
cone is blue in color and consists of gases undergoing com- 
bustion but with an insufficient supply of air ; the outer cone 
is but very faintly luminous and the combustion is there 
complete. The space between the outer and middle cone is 
filled with hot combustible matter which displays great 
reducing or deoxidizing power, especially is this so at the 
point of the second cone; this flame is accordingly called 
the reducing flame. Nearly any metallic oxide placed just 
in the tip of this cone is deprived of its oxygen and 
reduced to the metallic state. 

The highly heated air just beyond the point of the outer 
cone oxidizes very readily, hence this outer cone is termed 
the oxidizing flame. In the mouth blow-pipe it must be 
understood that the air is not propelled from the lungs, but 
simply from the mouth by the muscles of the cheek. The 
current of air may be produced by a bellows or other 
mechanical means. 

Oxy hydrogen Flame. By forcing a stream of pure oxygen 
through a gas flame, a blow-pipe flame of very high temper- 
ature may be produced. A flame from a mixture of hydro- 
gen and oxygen in proper proportions gives the highest 
temperature obtainable by chemical means . In the production 
of the oxyhydrogen flame, the gases (hydrogen and oxygen) 
are usually led by tubes from separate holders to the jet or 
blow-pipe where they are burned and allowed to mix only 
just before burning. Special precautions are made in the 
blow-pipe so that the mixture can not there explode. 

Safety Lamps. The temperature to which a gas must be 
raised in order that combustion may take place has already 
been defined as its ignition point, commonly called the kind- 
ling point. Combustion can not take place until this tem- 
perature is reached and if the temperature of the burning gas 
be reduced below this point the flame will be extinguished. 



108 

This fact may be simply illustrated with the candle flame by 
coiling 1 a thin copper wire into a cylindrical spiral about one- 
half an inch long* and of such diameter as to coincide with 
the flame-cone. If the coil be placed over the candle the 
flame will be extinguished, but if the coil be first heated and 
then placed over the flame it will shoot above the coil and 
continue to burn. 

A copper wire-gauze of sufficiently fine meshes may be 
placed over a gas jet and the flame will not extend above 
the gauze, or if the gas be lighted above the gauze the flame 
will not pass below. In each of these cases the temperature 
of the burning gases is reduced below the kindling point and 
combustion ceases. 

Different substances have different ignition points and 
owing to this fact a wire-gauze through which a marsh gas 
flame will not pass readily, permits the passage of the hydro- 
gen flame. 

The above considerations make clear the principles of 
safety lamps. The most celebrated of these is Davy's 
miners' lamp. This is an oil lamp the flame of which is 
enclosed in a cage of wire gauze made double at the upper 
part where the heat of the flame is most felt. The gauze has 
400 or 500 meshes to the square inch. The lamp is so 
arranged that the reservoir can be supplied with oil and the 
wick trimmed without unscrewing the cage and thereby 
exposing the flame of the lamp. 

In an explosive atmosphere of marsh gas and air, the fire- 
damp may burn within the cage but the flame will be extin- 
guished by the gauze and not ignite the mixture outside. 

The lamp thus serves to give indications of the state of 
the atmosphere in a mine and enables an examination to be 
made without risk to the inspector. This is the true use of 
the lamp and it is not intended to enable workmen to labor 
in an explosive atmosphere. 



109 

Stephenson' 's Lamp. Stephenson's original safety lamp 
was constructed upon the principle that the explosive mix- 
ture could be carried by the flame so rapidly that there 
would not be time for the mixture to be raised to the igniting" 
point. This rapid flow of the gases was accomplished by a 
tall chimney producing a powerful draught. If the velocity 
of the gases be greater than the rate of propagation of 
combustion in the mixture the flame will not spread. This 
principle has already been referred to in explaining the 
hollow structure of the Bunsen flame. 

The explosions which have so often proved disastrously 
fatal in coal mines and which the safety lamp is intended to 
help prevent, have in most cases been due to explosive 
mixtures of marsh gas, other hydrocarbons, and hydrogen 
with the air. Fine coal dust in the air of the mine increases 
the liability to explosion and in some cases this dust has 
been the sole cause of explosion. 

Explosions have occurred in flour mills through the 
general diffusion of flour dust throughout the building. Any 
readily combustible substance thickly distributed as fine 
dust through the air will burn with explosive effect. 

Slow and Flameless Combustion. There are several sub- 
stances which possess the power of causing the slow 
combustion of certain gases. Finely divided platinum or 
even platinum foil will bring about the combination of 
hydrogen and oxygen. A clean thin strip of platinum foil 
put into a jar containing a mixture of hydrogen and oxygen, 
will immediately cause their combination to begin, and if the 
foil be very thin its temperature may rise to redness and 
cause the explosion of the remaining mixture. 

If the platinum be reduced to the state of minute division 
as is the case of platinum black or its surface greatly 
extended as in spongy platinum, it immediately becomes red 
hot in a mixture of hydrogen and oxygen. Eydrogen falling 
upon platinum black in air is immediately ignited. Upon 



110 

this principle lamps for m^Gsteigous^ light have been 
constructed. 

If a thin piece of platinnm foil be heated but not suffi- 
ciently to emit light, and held in a jet of gas escaping from a 
Bunsen burner, its temperature will rise to redness and it 
will continue to glow as long as the mixed gases impinge 
upon it. This is a case of nameless combustion. The same 
result may be brought about in vapor of alcohol and ether. 

Although platinum possesses this property to a marked 
degree, it is not limited to this metal; palladium and gold 
display it to a less degree while glass and certain stones 
show it to a still lower degree. 

A full explanation can not be given of these results, but 
they are due to the property which the solids possess of con- 
densing gases upon their surfaces or of absorbing them and 
bringing them under the temporarily changed conditions 
within their sphere of mutual action. 

When the ignition point of a substance is lower than the 
temperature produced by its combustion, it will burn when 
once ignited ; but when the reverse is the case there will be 
required a continual application of external heat to keep up 
the combustion. 

SILICON. 

In many of its chemical relations silicon resembles 
carbon, but while the latter is the characteristic element 
of the organic kingdom the former is one of the most abun- 
dant elements of the mineral world. 

Silicon is not known to occur in the uncombined state, 
but in combination it is next to oxygen the most abundant 
and widely distributed element. In combination with oxygen, 
as silicon dioxide (silica), it occurs in sand and the various 
forms of quartz, which are among the most common and 
abundant forms of natural minerals. It also exists very 
widely in the silicates which result from the combination of 
silica with various metallic oxides. These silicates form the 



Ill 

great mass of the rocks which make up the earth's crust. 

Silicon oxide is also found in certain species of the vegetable 

kingdom. 

The element silicon is of no practical importance; it has been 
obtained both in the amorphous and crystalline forms, being in the 
first a dark brown powder and in the second of a metallic lustre resem- 
bling graphite. The powder burns vividly in oxygen until covered by 
a coating of silica; the graphitic form is incombustible. The amor- 
phous form readily attacks platinum when heated with it. It is claimed 
by some that there is a third form of silicon corresponding to the dia- 
mond form of carbon. 

Preparation of Silicon. Silicon may be prepared by decomposing 
potassium silico-fluoride at high temperature by potassium as indica- 
ted by the reaction, K 2 SiF e +K 4 — Si+6KF. After cooling the potas- 
sium fluoride is dissolved out by water. 

SILICA; Si0 2 . 

The only oxide of silicon, silica (Si0 2 ), is a very import- 
ant compound. Alone or in combination it forms a very 
large proportion of the earth's crust. The purest natural 
form of silica is rock crystal, a clear transparent variety of 
quartz. The dense white varieties of sand are nearly pure 
silica ; in a less pure form silica and the silicates constitute 
the greater part of nearly all soils. Its action in soils seems 
to be mainly mechanical as silica takes but little part in the 
direct sustenance of plants. It serves as a receptacle or 
basis through which the other ingredients of the soil are dis- 
tributed. Its chemical and physical stability admirably fit it 
for this purpose. Silica is found in the outer sheaths of cer- 
tain grasses and reeds and as tabasheer in the joints of the 
bamboo. This fact proves its solubility to a certain extent 
otherwise it could not be taken up by plants. Many hot 
springs and geysers also dissolve it. It is deposited in large 
quantities by the springs and geysers of the Yellowstone 
Park. 

The natural varieties of silica are insoluble in pure water 
but hot alkaline solutions readily dissolve the amorphous 



112 

varieties and under high temperature and pressure also dis- 
solve many of the crystallized forms. 

Silica is essentially an acid oxide forming salts with many 
metallic oxides. Owing to its non- volatility, it decomposes 
all salts of volatile acids when highly heated with them. It 
thus replaces acids which at a lower temperature displace it. 
When heated with bases, silica generally unites with them 
forming silicates. The silicates are the most common and 
abundant of minerals. As feldspars and micas the silicates 
enter largely into the composition of granitic rocks and the 
different varieties of clay are hydrous silicates of aluminum. 
Common glass is a mixture of several silicates. The silicates 
as a class are all insoluble except certain alkaline silicates in 
which there is a large proportion of the base. 

Silicic acid is generally represented as tetra-basic and the 
formula written H 4 Si0 4 , or Si0 2 with 2H 2 0, but the formulas 
of many of the silicates indicate their derivation from silica 
combined with more or less than two molecules of water. 

A compound consisting of silicon and carbon (SiC) can 
be prepared by heating silica with carbon in an electric 
furnace. The compound is called carborundum and has 
come into considerable prominence lately as an abrasive. It 
is made in large quantity at Niagara Falls. 

BORON. 

This element has not been found in the free state. In combination 
it is almost entirely confined to the mineral kingdom though its pre- 
sence has been detected in grape Tines and a few other plants. It is the 
basis of boric acid in which combination it is found in certain volcanic 
waters and forming many borates of the metals, one of the most 
important and common of which is sodium borate or tincal. 

The element may be obtained by heating boron trioxide with 
potassium. B 2 3 +3K 2 — B 2 -f 3K 2 0. In this manner boron is obtained 
as a dark brown powder. 

Boric Oxide and Acid. Boron forms but one oxide the formula of 
which is B 2 3 . This oxide forms three oxy-acids. The native acid 
found in volcanic regions is tribasic represented by the formula 3H 2 0, 
B 2 O s or H3BO3, but is converted into other forms by the action of 
heat; at red heat all the water is driven off. 



113 

The acid is an antiseptic and is sometimes used alone or with glycer- 
ine to preserve meats and other food. The solution of the acid in 
alcohol imparts a green color to the flame of the vapor. It will give 
color to steam issuing- from a boiling solution of the acid if a flame be 
held in the steam. 

Borates. At high temperature boric oxide combines with many 
metallic oxides giving glassy borates which often have characteristic 
colors — upon this property depends the main use of boric acid in the 
arts. The formulae of most of the borates do not indicate their deriva- 
tion from a tribasic acid. Borax or sodium borate is one of the most 
important of this class of salts. Borax occurs native in tincal. It is 
readily prepared by the action of boric acid on sodium carbonate. It 
will be further mentioned under sodium. 

COMPOUNDS OF HYDROGEN AND NITROGEN. 

Ammonia (NH 3 ). This is a compound of hydrogen and 
nitrogen indicated by the formula NH 3 . It is primarily 
of organic origin and results from the putrefaction of 
organic matter, from the destructive distillation of coal, 
bones, and other organic matter. It is constantly removed 
from the air through absorption by rain and by the soil. It 
has been found in the emanations of volcanoes. In the com- 
bined form it is frequently present in beds of guano (the 
excrement of sea fowls) and as the chloride and sulphate in 
certain volcanic regions. It is also present in small quantity 
as carbonate, nitrites, and nitrates in soils and water where, 
in the last named forms, it becomes available for plant food. 

Animals during life, and both plants and animals after 

death return to the air in the form of ammonia the nitrogen 

which existed in their organisms and possibly some of it is 

returned as free nitrogen. They thus return to the air the 

ammonia which was taken from it. The manner in which the 

nitrogen of the air was originally made available for food and 

started upon its endless circuit has been difficult to determine 

and even now is not thoroughly understood. It has lately 1 uvn 

found that certain species of bacteria exist which are 

capable of oxidizing the nitrogen of the air and thus starting 

it upon the cycle of plant service. One form of these 
8 



114 

bacteria is found to ply its vocation in connection with the 
growth of leguminous plants having" their homes in the roots 
of the plants. It is also found that bacteria are instrumental 
in transforming the nitrogen of dead organic matter into 
available shape for plant use again. 

Physical Properties of Ammonia. Ammonia is a color- 
less gas, having a strong, pungent odor which excites to 
tears. It has a caustic, burning taste. Its specific gravity 
is eight and one half referred to hydrogen. It is liquefied by 
a temperature of — 40° C. at atmospheric pressure, or by a 
pressure of six and one half atmospheres at 10° C. In the 
liquid state it is a colorless mobile liquid which at 0° C. has 
a specific gravity .62. Its boiling point is — 33. 7° C. under 
atmospheric pressure. 

During the evaporation of liquid ammonia great reduction 
of temperature takes place and it has for this reason been 
frequently used in the artificial production of cold for 
freezing, or other purposes. 

Gaseous ammonia is more readily soluble than any other 
gas, water at 15° C. dissolving over 750 times its volume, the 
volume of the solution being something more than one and 
one half times that of the water. 

During the solution of the gas more heat is evolved than 
corresponds to the liquefaction of the gas, which can only be 
attributed to chemical action. The gas however can be 
entirely removed from the water and no definite compound 
of the two is known. The solubility of the gas increases as 
the temperature of the water diminishes. The great solu- 
bility of ammonia in water may be strikingly illustrated by 
filling a bottle with ammonia by displacement over mercury, 
making the mouth of the bottle air-tight and transferring to 
a vessel of water; when the stopper is removed the water 
immediately fills the bottle and if the water be admitted by a 
tube through the cork it will play as a fountain. 

In Carre's freezing apparatus for ice, liquid ammonia is 



115 

allowed to evaporate from a strong" iron receiver which sur- 
rounds the water to be frozen. The vapor of the ammonia 
is absorbed by water contained in another receptacle, so as 
to increase the rapidity of evaporation from the receiver. 
The ammonia can then be driven ont of the water in the 
second vessel by heat and condensed by its own pressure in 
the receiver and the operation repeated. The boiler is of 
course allowed to cool before evaporation from the receiver 
begins. 

Chemical Properties of Ammonia. Ammonia is alkaline 
to a very high degree ; it has the alkaline action on vege- 
table coloring matter and combines with acids, neutralizing 
them completely. It can be kindled in the air, but will not 
continue to burn when the external source of heat is 
removed. In an atmosphere of pure oxygen the ammonia 
burns with a continuous flame. 

It is decomposed into its elements by passage through a 
red hot tube, two volumes of ammonia producing one volume 
of nitrogen and three volumes of hydrogen. Ammonia 
escaping into an atmosphere of chlorine takes fire and burns 
producing ammonium chloride. 

Its solution is largely used in the arts and as a reagent in 
the chemical laboratory. By neutralizing the solution of 
ammonia with the mineral acids, salts are obtained bearing- 
strong resemblance to the corresponding salts of sodium and 
potassium. This taken in connection with the other strong- 
alkaline characters, has given rise to the suggestion that the 
solution of ammonia contains an alkaline hydroxide (XH 4 
OH) similar to KOH and NaOH, in which NH 4 performs the 
same function as potassium and sodium. 

This hypothetical radical (NH 4 ) is called ammonium. 
The salts from the solution of ammonia may be considered 
as formed either by the direct union of ammonia with the 
acids or by the replacement of the hydrogen of the acid by 
ammonium; in the latter case ammonium acts similarly to 



116 

the metals in forming" salts. The salts of ammonium will be 
more fully described in connection with the metallic salts. 
Ammonia is easily expelled from its salts by heating with 
slaked lime or a solution of potash or soda. On account of 
its striking* odor this gives a ready test for such a salt. 

Preparation of Ammonia. There are many sources 
from which ammonia may be obtained, but the chief 
source is the ammoniacal liquor of the gas-works. The 
manufacture of gas will be described later, at present 
it is sufficient to know that ammoniacal liquor results 
from the destructive distillation of coal in the manu- 
facture of gas. This liquor contains several compounds 
of ammonia, two of the most important of which are the 
carbonate and hydro srilphide (NH 4 ) 2 C0 3 , and NH 4 HS. 
The liquor containing these substances is heated with lime in 
a still, the lime displaces the ammonia from combination 
and it is conducted into a tank containing sulphuric or 
hydrochloric acid. The acid combines with the ammonia 
forming ammonium sulphate or chloride, depending upon 
the acid used. There is always some hydrogen sulphide 
driven on 2 in the operation, but this escapes from the receiv- 
ing tank and is burned. 

The sulphate of ammonia is the form in which the 
ammonia is generally sold for fertilizing. The chloride after 
purification by heating and sublimation is used for various 
purposes and is the form generally used to give pure 
ammonia. From the chloride, ammonia is readily obtained 
by heating it with powdered lime as indicated by the reaction, 
2NH 4 Cl+CaO=CaCl 2 +H 2 0+2NH 3 . 

The gas may be conducted into a vessel of water until a 
solution of the required strength is obtained. By this means 
liquor ammonia is prepared as an article of commerce. 

The most convenient way of obtaining ammonia for labo- 
ratory purposes is to gently heat liquor ammonia; the gas 
passes from the solution Very readily and may be collected 



117 

by downward displacement or over mercury. The gas may 
be readily prepared for laboratory nse directly from the 
chloride as above indicated if the liquor ammonia be not on 
hand. 

In the above method of separating the ammonia from the 
ammoniacal liquor of the gas-works, the ammonia was dis- 
placed from its combination by another base, lime being 
used. It is possible (and sometimes done) to treat the 
ammoniacal liquor with an acid (sulphuric or hydrochloric) 
which combines with the ammonia and liberates carbon 
dioxide and hydrogen sulphide. But the sulphate or chloride 
thus produced is mixed with many other constituents of the 
liquid and is more difficult to purify. 

Other sources for the commercial preparation of ammonia 
are the blast furnaces and coke ovens ; the ammonia in these 
cases also resulting from the destructive distillation of coal. 

Although the direct combination of nitrogen and hydro- 
gen is only acconfplished with difficulty, this compound is 
sometimes produced when nitrogen is brought into contact 
with nascent hydrogen. 

Hydrozine or Hydrozoic Acid. There are two other compounds of 
nitrogen and hydrogen hydrozine (N 2 H 4 ) and hydrozoic acid (N 3 H), 
but they have up to the present time received no useful application. 

COMPOUNDS OF NITROGEN AND OXYGEN. 

These elements under ordinary conditions show no dispo- 
sition to enter into combination, however there are rive 
distinct compounds of them known; viz., N 2 0, NO, N 2 O b >, 
N0 2 =N 2 4 , and N 2 5 . These formulae show that the quanti- 
ties of oxygen that unite with a given quantity of nitrogen 
are to each other as 1:2:3:4:5. 

There are three oxy-acids of nitrogen corresponding to 
the first, third and fifth of these oxides. 

The compositions of these acids and their relations to the corres- 
ponding oxides will be seen from the following formulae; 



118 

N N 

^O Hyponitrous anhydride. |tO Hyponitrous acid. 

^ T qO Nitrous anhydride. ^ O Nitrous acid. 

^q 2 Nitric anhydride. h° 2 ° Nltric acid - 

The first two acids have not been obtained in a free or pure state 
and are known from their salts. 

The third is the most important of these acids and is the 
one from which all the compounds of nitrogen and oxygen 
are obtained directly or indirectly. 

NITRIC ACID. 

Preparation. The combination of oxygen and nitrogen 
can be brought about directly by artificial means, and in the 
presence of water nitric acid results but the acid is always 
prepared from natural nitrates. 

The manufacture of nitric acid is a commercial process 
and is accomplished by heating sodium nitrate with sul- 
phuric acid in suitable retorts, usually in cast iron cylinders. 

The proportion of the reagents and the final reaction are 
indicated by the equation, 2NaN03+H 2 S0 4 =Na 2 S0 4 +2HN0 3 . 
The nitric acid vapor produced is conducted from the retorts 
into stoneware or other suitable receivers in which it is 
condensed, the receivers being cooled by water. During the 
operation some of the vapor of the nitric acid is decomposed 
thus, 2HN0 3 =H 2 0+0+2N0 2 , the last product being a red 
vapor which in the solution of the condensed acid gives it a 
yellowish-red color. 

Pure nitric acid is colorless, but if exposed to sun-light 
the above reaction takes place with the resulting color. The 
oxygen thus liberated exerts a pressure on the acid in the 
bottle and may result in ejecting some of the liquid when 
the stopper is withdrawn. The strongest acid in the com- 
mercial manufacture is obtained by using pure reagents and 
collecting the middle portion of the distillate separately. 
For the most concentrated colorless acid some other precau- 



119 

tions are necessary. The strength of the acid is indicated 
by the specific gravity ; the strongest has the specific gravity 
1.53, common aquafortis has the specific gravity of 1.30 and 
contains less than 50 per cent of acid. 

On a small scale in the laboratory the acid may be made 
from either potassium nitrate or sodium nitrate by heating 
the salt with sulphuric acid in a glass retort and condensing 
the acid in a flask cooled by a wet cloth. In the laboratory 
method it is better to use the reagents in the proportions 
indicated by the following reaction, KN03+H 2 S0 4 =KHS0 4 + 
HN0 3 , for this reaction requires lower temperature and the 
acid salt is more easily dissolved out of the retort than 
would be the normal sulphate, which would be formed were 
double the amount of nitrate used. A given quantity of 
Chili saltpetre will produce more acid than the same weight 
of common nitre. 

In India and other dry countries potassium nitrate occurs 
in certain places as an efflorescence on the surface of the 
soil. This is the principal source of nitre. Sodium nitrate 
or Chilian saltpetre occurs as immense beds along the 
northern coast of Bolivia and Peru. 

Properties of Nitric Acid. Nitric acid when pure is a 
colorless liquid which fumes strongly in the air owing to 
condensation of the acid vapor by the aqueous vapor of the 
air. It has a very choking, suffocating smell. It is very 
corrosive, the strongest acid produces painful sores when 
brought into contact with the skin, and the dilute acid turns 
the skin and other organic matter yellow. A drop of sul- 
phuric or hydrochloric acid will stain cloth red and the color 
may be partially or wholly restored by prompt application of 
ammonia while the stain of nitric acid is intensified by 
ammonia though the corrosive action is prevented. 

Under ordinary conditions strong nitric acid is weakened 
and weak nitric acid strengthened by boiling, until an acid 
of 6*8 per cent is reached when the whole distils over without 



120 

any change. If the pressure nnder which the distillation 
occurs be varied the strength of the distillate will also vary. 

Nitric acid is a powerful oxidizing agent, very few 
substances being able to withstand its action. Phosphorus 
dropped into a dish containing strong nitric acid is oxidized, 
often with such energy as to give name, P 2 5 being pro- 
duced. 

Sulphur is oxidized by hot nitric acid to sulphur trioxide 
S0 3 . Finely divided carbon or sawdust may be set on fire 
by strong nitric acid. 

Nitric acid acts upon some organic substances so readily 
as to inflame them. A small quantity of oil of turpentine 
poured upon strong nitric acid in an open capsule ignites 
with some violence. Hair or silk may be made to take fire 
by holding it in the vapor of boiling nitric acid. 

Nitric acid acts upon all the common metals except gold, 
platinum and aluminum. It generally forms nitrates but 
sometimes only oxidizes the metals. Owing to its strong 
oxidizing power hydrogen is never evolved by the action of 
this acid upon the metals. The hydrogen displaced by the 
metal is oxidized by the remaining acid present. It has been 
shown that if nitric acid is entirely free from nitrous acid 
it acts very slowly if at all upon many metals. 

In addition to the actions above named, nitric acid acts 
upon a variety of organic compounds, one or more atoms of 
the hydrogen of the organic compound being replaced by one 
or more molecules of N0 2 . The resulting compounds are 
nitro-substitution compounds and will be referred to again. 

Nitric acid is mono-basic. 

Uses. Nitric acid is of great importance in the arts; 
among its most important uses may be mentioned the manu- 
facture of coal-tar colors, the preparation of nitro-com- 
pounds which include nearly all the high explosives, of 
many nitrates used in the arts, and the refining of gold and 
silver. An alloy of copper with gold is readily detected by 



121 

touching" it with nitric acid when the copper present will give 
the green nitrate. 

It is remarkable that the dilute acid generally acts more 
readily than the concentrated. 

Nitrates. The nitrates constitute a very important class 
of salts. They are all decomposed by heat and are soluble 
in water (with unimportant exceptions). They are, like 'the 
acid, oxidizing agents. Powdered lead nitrate and charcoal 
may be exploded by a blow. Common nitre is used in gun- 
powder because of its oxidizing power and several other 
nitrates are employed in other explosives. 

The negative chemical properties of nitrogen, its little 
disposition to combine with other elements and its character 
as a permanent gas are probably at the basis of the insta- 
bility of its compounds, to which we shall have frequent 
occasion to refer. 

The nitrates being generally soluble the acid can not be precipitated 
and it is not so easily detected in solution as the other common mineral 
acids. The easiest test is as follows — add to the suspected solution in 
a test tube, a solution of iron sulphate ; then introduce below the 
mixed liquids concentrated sulphuric acid if there be present any 
nitrate, the sulphuric acid will liberate the nitric acid and the ferrous 
sulphate reduces it to N0 2 which colors the two liquids at the surface 
of their junction. 

Nitrous Oxide, Laughing Gas, N 2 0. This gas may be 
obtained by heating ammonium nitrate in a Florence flask 
fitted with cork and delivery tube. It may be collected by 
displacement over warm water or mercury. The nitrate 
should be heated gently or nitric oxide will be produced. 

Properties. N 2 is a colorless transparent gas with a 
slight odor and sweetish taste. It is more soluble than 
oxygen, water dissolving its own volume at 10° C. It sup- 
ports ordinary combustion like oxygen; the combustion is 
due to the oxygen, the nitrogen monoxide being decomposed 
and the nitrogen set free. Carbon burned to carbon dioxide 
in nitrogen monoxide produces more heat than when burned 



122 

ill oxygen which shows that heat is evolved in the decompo- 
sition of nitrous oxide and must have been consumed in its 
production. A substance which absorbs heat in its produc- 
tion is called endotliermic, one which gives it out exothermic. 
Laughing gas is used as an anaesthetic in dental surgery. 
It may be drawn into a test tube in the liquid state from the 
holder. The liquid supports combustion. It may be dis- 
tinguished from oxygen by its greater solubility and sweetish 
taste. 

Nitric Oxide, NO. This oxide is readily obtained by the action of 
dilute nitric acid npon copper. The metal is oxidized and the acid 
deoxidized with the separation of nitric oxide, the oxide formed is 
acted upon by another portion of the acid and copper nitrate is 
formed. The nitric oxide is a colorless transparent gas, but in con- 
tact with oxygen it unites with it, giving the nitrous oxide if the 
oxygen be in excess, otherwise some trioxide is formed, giving a very 
characteristic reddish brown vapor. The presence of oxygen may be 
readily detected by the addition of this gas. It will support combus- 
tion if the temperature of the burning body is high enough to decom- 
pose the gas. 

OTHER OXIDES OF NITROGEN. 

Nitrous Anhydride, N 2 3 . There is still some uncertainty as to the 
existence of this compound. The substance generally assumed to be 
X 2 3 is very probably a mixture of nitrous and nitric oxides. A solu- 
tion of the substance is believed to contain nitrous acid, though the 
acid has not been isolated. 

Nitrogen Tetroxide. This substance is the main result of the action 
of oxygen upon the nitric oxide. This gas possesses the property of 
combining directly with certain metals forming nitro-metals. The 
tetroxide will support combustion if the temperature of the burning 
body be high enough to decompose the gas. 

Nitrogen Pentoxide, N 2 5 . The pentoxide may be obtained by 
dehydrating nitric acid with phosphorus. It is a white crystalline sub- 
stance. It is very unstable and when suddenly heated explodes with 
violence. It dissolves in water forming nitric acid. 

CHLORINE; CI. 

Chlorine has not been found in the uncombined state in 
nature. It is a member of an important natural group 
including iodine, br online, and fluorine. On account of the 



123 

occurrence of the first three in the salts of sea water, the 
group has been called the halogens, and their compounds 
the haloid compounds. 

In combination with the metals, chlorine is of abundant 
occurrence, the most common chloride being" sodium chloride, 
common salt. In the Stassfurth deposits potassium chloride 
is also an abundant constituent. Many other chlorides occur 
native. 

The chlorides of sodium and potassium, especially the 
latter, are found in animal secretions. Chlorine is also 
found in combination with hydrogen as hydrochloric acid, in 
the gases issuing from certain volcanoes. 

Preparation of Chlorine. Chlorine may be extracted 
from common salt by heating a mixture of the salt and man- 
ganese dioxide with dilute sulphuric acid. The reaction is 
indicated by the equation 2NaCl+Mn0 2 +2H 2 S0 4 =Na 2 S04+ 
MnS(X+2H 2 0+Cl 2 . Chlorine may also be obtained from 
hydrochloric acid by gently heating manganese dioxide with 
it, as indicated by the equation, Mn0 2 +4HCl=MnCl 2 +2H 2 0+ 
Cl 2 . This gas is a very offensive one to deal with and special 
precautions and care should be taken in obtaining and 
manipulating it. On the manufacturing scale chlorine is 
obtained by the second method. 

Chlorine is now prepared on the manufacturing scale in 
Europe by the electrolysis of common salt. The same 
process is employed in this country to prepare sodium 
hydroxide but the chlorine, so far as can be learned, is 
wasted. 

Physical and Chemical Properties. Chlorine is a greenish 
yellow gas, with a specific gravity of 35.5 referred to hydro- 
gen. It has a disagreeable suffocating odor and is easily 
liquefied. At ordinary temperature water dissolves about 
two volumes of the gas. For experimentation chlorine is 
collected by displacement, or over tepid water; it acts upon 
mercury and there is considerable loss in collecting it over 



124 # 

cold water. A strong brine solution dissolves it much less 
readily than water. 

Chlorine has powerful affinities and unites with a great 
number of the other elements even at ordinary temperature. 
Its affinities do not extend to oxygen but are strongly exerted 
towards hydrogen and the metals. Its affinity for hydrogen 
is its most distinguishing characteristic. 

It combines directly with hydrogen, bromine, iodine, 
sulphur, arsenic and phosphorus. Phosphorus finely 
divided or a well dried piece, will take fire in chlorine; 
powdered arsenic dropped into the gas inflames. 

It combines directly and at ordinary temperature with 
nearly all the metals. Powdered antimony and several other 
metals in the form of thin leaf take fire when dropped into 
the gas. 

On account of its affinity for hydrogen a lighted wax taper 
plunged into the gas will continue to burn with a smoky 
flame, the hydrogen of the taper burning, the carbon being 
separated. 

For the same reason many of the hydrocarbons will take 
fire spontaneously ; a strip of bibulous paper wetted with oil 
of turpentine and plunged into the gas bursts into flame with 
a copious liberation of soot — a mixture of chlorine and 
acetylene explodes violently when exposed to light. 

Chlorine is not capable of direct combination with carbon, 
which fact accounts for the separation of the carbon in the 
cases just cited. 

On account of its attraction for hydrogen it will decom- 
pose water if the solution be exposed to light. A mixture of 
hydrogen and chlorine can be kept in the dark, but if 
exposed to diffused daylight they combine quietly, if to 
direct sunlight, they combine suddenly with explosion. 

Uses. The most useful applications of chlorine depend 
upon its affinity for hydrogen. Its most valuable property 
from an industrial point of view is its bleaching power. 



125 

Chlorine poured into a solution of indigo or other vegetable 
coloring matter will rapidly discharge the color. The same 
action is observed if cloth dyed with vegetable colors be 
dipped in a solution of chlorine. Colored flowers are 
bleached when dipped into a jar of the gas. 

For bleaching it is essential that water be present, as per- 
fectly dry chlorine does not even affect litmus. The chem- 
istry of the process seems to be due to the action of the 
chlorine upon the water, liberating the oxygen, which in 
connection with the chlorine converts the coloring matter 
into oxidized or chlorinized products, which are colorless or 
nearly so. 

Chlorine is largely used in the arts for bleaching linen 
and cotton goods and rags for the manufacture of paper. 
Silken and woolen goods would be injured by chlorine and 
are bleached with sulphurous acid gas. For bleaching pur- 
poses neither the gas nor its solution is so convenient as the 
combined form, hence it is generally employed in the form 
of bleaching powder called chloride of lime, from which the 
gas is easily liberated as desired. 

Chlorine is also one of the best deodorizers ; by virtue of 
its affinity for hydrogen it breaks up and removes from the 
air hydrogen sulphide and ammonia both of which result 
from the putrefaction of organic matter and are very ob- 
jectionable. Chlorine is also used as a disinfectant; its 
affinity for hydrogen and its oxidizing power enable it to 
destroy certain micro-organisms which are injurious to 
health. 

Liquid chlorine is now an article of commerce ; it is put 
up and transported in iron bottles lined with lead; it is used 
in the extraction of gold from its ores. 

HYDROCHLORIC ACID; HCI. 

Occurrence. It occurs in nature in the gases omitted 
from volcanoes and has also been found in the spring waters 
of volcanic districts. 



126 

Preparation. Hydrochloric acid may be produced by the 
direct union of the elements but for use it is always prepared 
by acting upon sodium chloride with sulphuric acid as 
indicated by the following reaction, NaCl+H 2 S04=NaHS0 4 
-fHCl; the gas may be collected by displacement or over 
mercury. By using the proper proportion of the ingredients 
and a higher temperature the reaction for the production of 
the acid can be made to take the form, 2NaCl+H 2 S0 4 = 
Na 2 S0 4 +2HCl. 

Hydrochloric acid was formerly obtained in enormous 
quantities as a bye-product in the Leblanc process of 
manufacturing sodium carbonate, the first step in the 
operation being indicated by the above reaction. The 
manufacturer of the alkali was compelled to prevent the 
escape of the liberated acid into the air because of its 
destructive action upon vegetation. Owing to changes in 
the methods of making alkali the hydrochloric acid is now 
a principal product in the Leblanc method. 

The acid vapors resulting from the action of the sulphuric 
acid upon the salt, are thoroughly cooled and then brought 
into contact with a large surface of water by which the 
acid is absorbed. 

Properties. Hydrochloric acid is a colorless gas with 
choking pungent odor. It fumes strongly in the air by con- 
densing the moisture there present. Its formula shows it to 
be heavier than air. It is very soluble in water, one volume 
of water at ordinary pressure and 0° C. dissolves 500 volumes 
of the gas. As is generally the case the solubility decreases 
as the temperature rises. The solubility of the gas may be 
illustrated in the same manner as with ammonia. 

The common liquid designated as hydrochloric acid is a 
solution of the gas in water, the strongest solution at 8° C. and 
ordinary pressure contains 43.8 per cent of the acid and has 
a specific gravity of 1.22. The strength of the acid may be 
inferred from its specific gravity. 



127 

If a weak solution of the acid be boiled, it loses water and 
becomes stronger; if a strong solution be boiled it loses acid 
and becpmes weaker until in each case the solution contains 
30 per cent of the acid when this solution distils over at a 
temperature of 110° C. This would seem to indicate a definite 
compound between the water and acid in the proportion 
named, but this proportion changes with the pressure. 

Commercial hydrochloric acid is usually yellow from 
impurities. It is very likely to contain some chlorine, some 
sulphuric acid, some arsenic, and some iron chloride. Mix- 
tures of snow or powdered ice and hydrochloric acid make 
very convenient refrigerants. 

Hydrochloric acid is readily liquefied by cold and pres- 
sure. The liquid acid is colorless, with a specific gravity of 
.9. The liquid acid is almost without action upon most of 
the metals which are readily attacked by the aqueous solu- 
tion. The liquid acid does not act upon lime. Dry hydro- 
chloric acid gas does not act upon calcium carbonate. 

Action of Hydrochloric Acid upon the Metals and Metal- 
lic Oxides. All the metals which decompose water will more 
readily act upon hydrochloric acid liberating hydrogen and 
forming a chloride. Sodium, potassium, zinc, iron, and tin 
are examples. Hydrochloric acid does not readily act upon 
aluminum and when boiling to a slight extent upon silver. 

The acid acts upon metallic oxides, forming a chloride 
and water, two atoms of chlorine replacing one atom of 
oxygen. Those oxides to which there are no corresponding 
chlorides (the less basic oxides) frequently evolve chlorine 
from the acid. Thus while the lower oxide of manganese 
forms manganese chloride (MnCl 2 ), Mn0 2 evolves chlorine; 
MnO+2HCl=MnCl 2 +H 2 0; MnO 2 +4HCl = Mn01 2 + 211-0+01,.. 
Of the common metals the dichlorides are soluble in water 
except the dichloride of lead, the monochlorides are soluble 
except those of silver and mercury. Any soluble chloride in 
solution gives upon the addition of silver nitrate a white 



128 

curdy precipitate of silver chloride, which blackens upon 
exposure to light and is readily soluble in ammonia. This is 
a very characteristic test for a chloride in solution. 

AQUA REGIA ; NITRO=MURIATIC ACID. 

This is a name given to a mixture of three volumes of 
hydrochloric acid and one of nitric acid. The mixture will 
dissolve gold or platinum while neither of the acids singly 
will do it. A chloride of the metal is formed and the power 
of the mixture depends upon the chlorine liberated. HN0 3 + 
3HC1=2H 2 0+N0C1+C1 2 . 

COMPOUNDS OF CHLORINE AND OXYGEN. 

Chlorine and oxygen have not been made to combine directly but 
there are known two oxides of chlorine and four oxy-acids ; the oxides 
are C10 2 and C1 2 0. The oxides are very unstable bodies and dangerous 
to handle because of their explosive character. 

The oxy-acids of chlorine are hypochlorous (HCIO), chlorous 
( HCIO 2 ), chloric ( HCIO 3 ), and perchloric (HCIOJ. The salts of the first 
and third are of considerable importance. Some of the metallic hypo- 
chlorites are useful in bleaching and potassium chlorate is of practical 
importance as an oxidizing agent ; these salts will be referred to under 
the metals from which they are formed. 

COMPOUNDS OF CHLORINE WITH CARBON, SILICON, BORON, 
AND NITROGEN. 

Although chlorine does not combine directly with carbon, several 
chlorides of carbon can be obtained by indirect means as by the action 
of chlorine upon the hydrocarbons one atom of chlorine removing and 
combining with one atom of hydrogen and another atom of chlorine 
taking the place of the removed atom of hydrogen. This mode of sub- 
stitution is called metalepsis. Chlorine combines directly with silicon 
and boron. With nitrogen it forms a very explosive compound indica- 
ted by the formula NC1 3 . This compound is formed by the action of 
chlorine upon ammonium chloride and is very dangerous to handle. 

BROMINE; Br. 

Occurrence. Bromine is not found free in nature. It 
occurs mainly in combination with potassium, sodium, and 
magnesium in small quantities in sea water; more abun- 
dantly in certain mineral waters as at Kissingen and in the 



129 

mother liquor of the salt works at Stassfurth, Germany, 
and of several of the salt works of the United States. 
Most of the bromine consumed in the United States comes 
from the mother liquor of the salt works in the United States 
and some from Stassfurth. It is obtained in greater quantity 
from the Ohio brine wells, and some from those of Pennsyl- 
vania, West Virginia and Michigan. 

Preparation. After the less soluble salts are separated from the 
mother liquor by evaporation and crystallization, the liquor is intro- 
duced into a still and acted upon by chlorine. The chlorine liberates 
the bromine which is distilled off by passing steam into the still. The 
chlorine may be produced in the same still or introduced from a separ- 
ate retort. 

Properties. Bromine is the only non-metallic element 
which is liquid under ordinary conditions ; it has a distinct red 
color; at 15° C. it has a specific gravity of 3. It emits an 
orange reddish acrid vapor which is very irritating and dis- 
agreeable, more so than that of chlorine. Three parts dis- 
solve in 100 parts of water by weight. In its chemical 
attributes it resembles chlorine; it combines directly with 
many metals and non-metals and bleaches like chlorine. 

Little use has been made of bromine since chlorine can 
generally be used for the same purposes and is much more 
abundant. It has, however, been used as a disinfectant, in 
the manufacture of coal tar dyes, and in analytical chemistry; 
for the last it is much more convenient than chlorine, being 
a liquid. For disinfecting the liquid is absorbed by cakes or 
sticks of kieselguhr or other porous earth made plastic by 
molasses. These sticks absorb a large amount of bromine 
and are kept in tightly stopped bottles. 

Several bromides are employed in medicine and in photo- 
graphy. Bromine is soluble in carbon disulphide and ether. 

Hydrobromic Acid; HBr. Bromine combines directly with hydro- 
gen forming hydrobromic acid (HBr). corresponding to hydrochloric 
acid (HG1). 

Oxy=Acids of Bromine. No oxides of bromine have boon obtained 
but there are two oxy-acids similar to the corresponding chlorine 
acids. Hypobromons acid (HOBr) and bromic acid (HBrO s ). 
9 



130 

IODINE; I. 

Iodine has not been fonnd in a free state; in nature it 
occurs in combination, principally with potassium, sodium, 
magnesium, and calcium as iodides or together with these 
metals and oxygen as iodates. Iodine is found in sea water, 
in many mineral waters, and as sodium iodate (NaI0 3 ) in the 
Chilian nitre beds. 

Preparation. The two principal sources of iodine are 
kelp (the ashes of sea weed) and the native Chilian saltpetre 
or "Caliche," the latter source now furnishes the greater pro- 
portion of iodine. 

Many varieties of sea-weed extract the iodine from sea water as a 
necessary portion of their food ; when these weeds are burned the 
iodine is left in the ashes or "kelp," together with a large number of 
other salts. The iodine is mainly in the form of iodides of sodium and 
potassium. These iodides are separated from the other salts as per- 
fectly as possible and then the iodine is liberated by the combined 
action of sulphuric acid and manganese dioxide exactly as chlorine is 
liberated from common salt. 

In the "Caliche " the iodine is in the form of sodium iodate (XaI0 3 j 
from which it is precipitated by the action of acid sodium sulphite. 

Properties. Iodine is a crystalline solid of a bluish black 
color resembling graphite. In the solid state its specific 
gravity is nearly 5. It volatilizes sensibly at ordinary tem- 
perature diffusing an odor resembling that of chlorine. It 
fuses at 114° C. and gives a beautiful violet vapor which is 
one of the heaviest known gases being nearly nine times 
as heavy as air. At a higher temperature the color of the 
vapor changes and its density becomes less. 

It is slightly soluble in water, readily soluble in carbon 
disulphide, benzene, petroleum spirit, and solution of potas- 
sium iodide and alcohol. 

In chemical properties it resembles chlorine and bromine 
but is less energetic being displaced from its compounds by 
these elements. It combines directly with many elements 
both metallic and non-metallic. Phosphorus placed in con- 
tact with powdered iodine at once takes fire, as also does 



131 

powdered antimony when dropped into iodine vapor. In the 
presence of water it attacks gold. When brought into con- 
tact with starch it gives a sky blue color; this is a very 
delicate test for free iodine and will reveal the presence of a 
millionth part in any liquid ; iodine in combination will not 
affect the starch. 

Uses. Iodine is largely used in the manufacture of 
aniline colors but the bulk of its compounds is used in 
medicine. A small quantity is also used in photography — 
the iodides of silver, potassium, ammonium, and cadmium 
being used for this purpose. 

The tincture of iodine is a mixture of iodine and potas- 
sium iodide dissolved in alcohol. Iodine dissolved in carbon 
disulphide gives a solution opaque to light but transparent 
to heat. To give the starch test the iodine must be in the 
free state and as it nearly always exists in combination, it is 
necessary to add to the liquid under examination some agent 
to liberate the iodine. The test is usually made by adding 
to the suspected liquid a little starch paste then a little 
chlorine water, the chlorine will liberate the iodine if present 
in the form of an iodide. Iodine is of course an equally 
delicate test for starch. 

Iodine can be combined directly with hydrogen to form hydrogen 
iodide or hydriodic acid ; this acid is very similar to hydrochloric and 
hydrobromic acids. 

Oxides and Oxy=Acids of Iodine. Iodine can be directly oxidized by 
ozone but the only oxide definitely known is I 2 O r> . Iodic acid (HI() 3 ) 
has been isolated. The periodic acid (HIC) 4 ) has not been isolated, but 
salts corresponding to the acid are known. 

Other Compounds of Iodine. Iodine combines with carbon, nitro- 
gen and boron forming compounds similar to the chlorine compounds 
of the same elements. 

Considering the chemical resemblance of chlorine, bromine, and 
iodine it is very remarkable that the elements all combine with each 
other. 

FLUORINE; F. 

Occurrence. Fluorine occurs in combined form as fluor-spar (CaF, ) 
— sometimes called Derbyshire spar on account of its abundant occur- 



132 

rence in Derbyshire. It is also present in the mineral cryolite a double 
fluoride of aluminum and sodium. In a small quantity it is present in 
a number of other minerals, in the bones, and in the enamel of 
teeth. Fluor-spar is the most abundant compound containing it. This 
mineral crystallizes in cubes or octahedrons with varying shades of 
color, some of which are very delicate and beautiful. 

Preparation and Properties. Fluorine was not isolated until 1SS6. 
It was then obtained by decomposing hydrofluoric acid i HF i by elec- 
tricity. It is a colorless gas and the most chemically active element 
known. On account of its intense disposition to combine with other 
elements, it resisted until recently all attempts to isolate it. It decom- 
poses water instantly and combines readily with mercury. It explodes 
with hydrogen even in the dark, and combines with combustion with 
many non-metals, attacks the metals, and even attacks glass. No com- 
pound with oxygen is known. 

Hydrogen Fluoride; HF. This is the most important compound of 
fluorine. The pure acid can be obtained by heating acid potassium 
fluoride in a platinum retort with platinum tube and condensing 
arrangement cooled by a freezing mixture. The acid thus obtained is a 
colorless liquid a little lighter than water. It has a strong affinity for 
water and produces a hissing noise when brought into contact with it. 
A solution of hydrofluoric acid in water is obtained by heating pow- 
dered calcium fluoride i GaF 2 1 with sulphuric acid.. CaF 2 +H 2 S0 4 = 
0aSO 4 +2HF. This operation is performed in a leaden retort with tube 
and condenser of the same metal, the condenser being cooled by a 
freezing mixture. This solution possesses powerfully acid properties 
and the vapor escapes rapidly from the water as the temperature rises. 

The dilute acid dissolves all ordinary metals except platinum, gold, 
silver, mercury, and lead. It also readily attacks glass if the least 
moisture be present, though it has been found that the anhydrous acid 
does not affect glass. 

Uses. The principal use of hydrofluoric acid depends upon its 
power of acting upon silica and the silicates. Powdered sand maybe 
dissolved in the aqueous solution of the acid and if the solution be 
evaporated the silica will volatilize as silicon fluoride (SiF 4 1. If a sili- 
cate be digested and heated with the acid a fluoride of the base will be 
left. 

The action of the acid upon glass is explained by its power of 
attacking silica, for glass is a mixture of two or more silicates. 

A design may be etched or engraved upon glass as follows : let the 
plate be coated with wax or etching-ground and the design drawn 
with a pointed instrument cutting through the wax. The plate is then 
placed with the waxed side down over a shallow leaden dish which 
contains calcium fluoride and sulphuric acid. Upon the application of 
a little heat the acid is disengaged and speedily makes the impression 



133 

upon the glass. If the engraving- is done with the vapor of the acid, 
the design is dull or opaque ; if the liquid acid is employed the lines are 
transparent. 

The gaseous acid does not produce an uniform opacity and is there- 
fore not generally suitable for the purpose. For opaque etchings a 
solution of the acid fluorides of the alkalies is used, usually one contain- 
ing some potassium or ammonium sulphate. 

SULPHUR; S. 

Occurrence. This is an elementary body of great import- 
ance. It occnrs abundantly in the free state and also as a 
constituent in many combined forms. In the uncombined 
form it is usually though not invariably found in volcanic- 
regions. In some localities sulphur is being deposited from 
chemical actions now taking place. These are called "living- 
sulphur beds" and occur in the regions of geysers, hot 
springs, fumaroles, and other evidence of recent volcanic- 
activity. 

The free sulphur is also found disseminated through 
stratified deposits alternating with beds of clay or other 
minerals. 

Sicily produces the greatest amount of native sulphur. 
It is also found in our own country in California, Nevada, 
Wyoming, Arizona, and Utah. The mines at Cove Creek, 
Utah, supply a considerable amount of sulphur. It occurs 
in many other places throughout the world. 

In the combined form it occurs as the sulphide of many 
metals, the most important being iron pyrites, FeS 2 ; copper 
pyrites, CuFeS 2 ; galena, PbS; zinc blende, ZnS; and cinna- 
bar, HgS. It occurs in sulphates and in hydrogen sulphide 
in many mineral waters. 

It occurs in many natural sulphates, the most important 
being those of calcium, lead, strontium, magnesium, and 
sodium. 

Extraction of Sulphur from Native Sulphur. Liffnatiou 
Process. All native sulphur must be separated from the 
mineral impurities which accompany it. This is usually 



134 

done by the lignation process or melting out the sulphur and 
there are several ways of accomplishing this. The sulphur 
ore is sometimes made into a kiln and the sulphur is melted 
out by smothered combustion, a portion of the sulphur itself 
being consumed to furnish the heat. This method though 
wasteful as regards sulphur is cheap in other respects and is 
employed to a large extent. The heat for driving out the 
sulphur may be obtained from extraneous fuel. High pres- 
sure steam has also been employed for melting sulphur out 
of its ores; in this case the ores are subjected to the action 
of the steam in closed iron vessels. A solution of calcium 
chloride in water with boiling point at 120° C. is sometimes 
used for furnishing the heat to melt out the sulphur. 

Distillation Process. The ores of sulphur are sometimes 
enclosed in retorts and subjected to distillation, the sulphur 
being condensed in the liquid state. 

Purification of the Crude Sulphur. Sulphur obtained by 
any of the above processes usually contains a few per cent 
of earthy impurities from which it is freed by distillation. 
If the vapor of the sulphur is condensed in a chamber 
below the melting point, it gives a pale yellow powder 
known as sublimed or flowers of sulphur. When the tem- 
perature of the chamber rises sufficiently high the flowers 
melt and are run out into sticks giving the roll sulphur or 
brimstone. If the vapor of sulphur be conducted directly 
into a condenser kept cool, the sulphur is deposited in a 
liquid state giving brimstone which is said to differ slightly 
from that first named. 

Extraction of Sulphur from the Sulphides. Sulphur was 
formerly obtained in considerable quantity from iron sul- 
phide (FeS 2 ) by heating it in the absence of air. At a very 
high temperature nearly one-half the sulphur can be 
separated, but at ordinary furnace heat only about one- 
fourth is separated. This method of preparing sulphur has 



135 

practically ceased as a manufacturing industry, the pyrites 
being used for making sulphuric acid. 

Sulphur can also be obtained from copper pyrites by 
roasting with proper precautions. This is sometimes done 
in the process of roasting the ore preliminary to the extrac- 
tion of the copper. 

The sulphur from the pyrites is generally found to 
contain impurities associated with those minerals and is 
purified by subsequent treatment. 

Sulphur from Other Sources. Sulphur is obtained in some quan- 
tity from the waste products of the gas works and in still greater 
amount from the waste products of the alkali works. Its presence in 
these products will be explained subsequently. 

Physical Properties of Sulphur. As ordinarily seen sul- 
phur is a lemon yellow, brittle, crystalline solid, insoluble in 
water but soluble in carbon disulphide. It exhibits several 
allotropic modifications the two most characteristic of which 
are marked by their action with the same solvent — one form 
being soluble in carbon disulphide the other form not. 

The soluble varieties of sulphur show two distinct crystalline 
forms ; one the native form of sulphur is the rhombic octahedron, the 
same form which results when it crystallizes from solution ; the other 
is the oblique prismatic which results when it cools after melting. The 
distinction between these crystalline forms extends to their fusing 
points and their specific gravities, the first having the higher specific 
gravity but lower fusing point. 

The insoluble form of sulphur shows several uncrystalline varieties, 
the most important of which are the ductile and the amorphous. The 
ductile sulphur results when boiling sulphur is poured in a thin stream 
into water; it is soft and elastic like rubber. The amorphous sulphur 
is always formed when the flowers of sulphur are deposited and will be 
left undissolved if the flowers be treated with carbon disulphide. Milk 
of sulphur is a soluble amorphous form of sulphur obtained by pre- 
cipitation by the addition of an acid to an alkaline solution of sulphur. 
This form is white and milky in appearance and is a medicinal 
preparation. If a solution of sulphur dioxide 4 be decomposed by 
electricity sulphur appears at. the negative pole as an Insoluble 
amorphous variety, while if a solution of hydrogen sulphide be 
electrolysed the sulphur appears at the positive pole as a soluble 
amorphous variety. For this reason the soluble varieties have been 
classed as electronegative and the insoluble as electropositive. 



136 

Chemical Properties. Sulphur possesses energetic affini- 
ties combining directly with a large number of elements. 
Many of the sulphides in atomic constitution correspond 
with the oxides of the same elements. Any modification of 
sulphur heated in the air or oxygen takes fire and burns with 
a pale blue flame producing sulphur dioxide. Finely divided 
sulphur, especially flowers of sulphur, is slowly oxidized in 
moist air yielding sulphuric acid. 

Sulphur in a finely divided state will combine with some 
of the metals at ordinary temperature and at a high temper- 
ature it will combine with nearly all the metals and with all 
the non-metals except nitrogen. It can very readily be made 
to display electrical properties as may be shown by friction 
or by powdering in a dry mortar. 

COMPOUNDS OF SULPHUR AND HYDROGEN. 

There are at least two compounds of hydrogen and sulphur. The 
most important, hydrogen sulphide, is analogous in composition to 
water haying the formula H 2 S. The other, hydrogen persulphide, 
contains a larger proportion of sulphur. Its formula has not been 
definitely determined but is thought to be H 2 S 2 though it may contain 
a larger proportion of sulphur. There are reasons for thinking that 
still more complex compounds exist. 

HYDROGEN SULPHIDE; H 2 S. 

Occurrence. This gas is present in the waters of many 
springs, which has caused them to be called sulphur springs 
and such mineral water sulphur water. It is found in large 
quantity among the gases issuing from volcanoes. It is very 
generally present among the products which result from the 
putrefaction of organic matter containing sulphur, both 
animal and vegetable. The offensive odor of rotten eggs is 
mainly due to it and it generally contributes to the unpleas- 
ant odors from sewers and drains. The gas is also found 
among the products of the destructive distillation of coal 
and other organic substances containing sulphur. 



137 

Properties of Sulphuretted Hydrogen. It is a colorless 
gas with the odor of putrid eggs and faintly sweetish taste. 
It is liquefied by a pressure of seventeen atmospheres. 
Water at ordinary temperature dissolves about three times 
its volume. The aqueous solution is acid to test paper and 
has the taste and smell of the gas. The gas is readily com- 
bustible giving the blue flame of sulphur. When the supply 
of oxygen is abundant the products of the combustion are 
water vapor and sulphur dioxide — 1128+03=1120+802 — and 
when mixed with oxygen in the proportions indicated, and 
ignited, the mixture explodes. If the supply of oxygen be 
limited some of the sulphur will be deposited. 

In the presence of moisture and oxygen the gas is 
decomposed with the deposition of sulphur hence the solu- 
tion of the gas in water can not be kept for a great while ; 
light produces the decomposition. The gas acts as a poison 
if inhaled in large quantities and even when much diluted 
with air it gives rise to disagreeable symptoms. 

Hydrogen sulphide is decomposed into its elements at a 
temperature a little above 400° C. Chlorine and bromine 
decompose it at ordinary temperature, removing the hydro- 
gen and depositing the sulphur. On account of its ready 
decomposability hydrogen sulphide acts as a reducing agent, 
thus when heated with concentrated nitric or sulphuric acid 
the hydrogen is oxidized and the sulphur deposited. 

Action with the Metals and Metallic Oxides. Many of the 
metals and metallic oxides act upon sulphuretted hydrogen 
in a manner resembling the action of the other hydrogen 
acids. With some of the metals as mercury, silver, and 
lead, this action takes place at ordinary temperature. When 
heated in the gas several other metals decompose it. It is 
because of its action upon silver that silver plate and other 
articles of silver often tarnish; silver egg spoons are 
blackened by the sulphur present in the eggs. 

Hydrogen sulphide acts upon many metallic oxides form- 



138 

nig metallic sulphides and water according to the general 
formula, MO+H 2 S=MS-fH 2 0. 

Action of Hydrogen Sulphide with Metallic Salts. Hydro- 
gen sulphide is one of the most valuable reagents in the 
chemical laboratory because of its disposition to act upon 
solutions of metallic salts. When hydrogen sulphide is 
brought into contact with solutions of metallic salts, charac- 
teristic precipitates are often formed. These precipitates are 
insoluble sulphides produced by the mutual decomposition 
of the dissolved salt and the hydrogen sulphide, some acid 
being produced at the same time due to the combination 
of the acid radical of the salt with the hydrogen liberated 
from the hydrogen sulphide. This action may be repre- 
sented by the general equation, 2MR-f H 2 S=2HR+M 2 S. 

All metals are thus precipitated from their solutions 
provided their sulphides are insoluble in the products of the 
reactions — water and dilute acid. Those metallic sulphides 
which are soluble in or decomposed by dilute acid would of 
course not be precipitated by the reaction above indicated. 
Any metals whose sulphides are soluble in acid solu- 
tions, may be precipitated from the solutions of their 
salts by the use of an alkaline sulphide instead of hydrogen 
sulphide. The alkaline sulphide generally used for the 
purpose is ammonium sulphide (NH 4 ) 2 S and the action is 
indicated thus, 2MR+(NHJ 2 S=M 2 S+2NH 4 R. From this 
reaction it will be seen that no acid is liberated and if the 
metallic sulphide represented in the second member is 
insoluble in the products of the reaction, it will be pre- 
cipitated. 

The metals may accordingly be divided into three classes — 1. Those 
whose sulphides are soluble in water; 2. Those whose sulphides are 
insoluble in water and dilute acid ; 3. Those whose sulphides are solu- 
ble in dilute acids but insoluble in water and dilute alkaline solutions. 
The first class is not affected by hydrogen sulphide ; the members of the 
second class are precipitated from a solution of their salts by hydrogen 
sulphide and those of the third by the addition of ammonium sulphide. 



139 

The sulphides of the different metals often have very 
characteristic colors, which taken in connection with reac- 
tions when treated with certain reagents, give the means of 
distinguishing and thus determining the metal present in 
a given solution. 

The action of hydrogen sulphide with the oxides and salts 
of lead explains the discoloration of lead paint which so fre- 
quently occurs. Any paint in which lead is an ingredient is 
liable to discoloration by hydrogen sulphide due to the forma- 
tion of lead sulphide. Paintings so discolored are sometimes 
partially restored by continued exposure to light and air, the 
lead sulphide being converted into lead sulphate. The 
presence of hydrogen sulphide in gas may be detected by 
moistening a paper with a solution of lead nitrate or lead 
acetate and exposing it to the action of the gas. The paper 
is blackened if a trace of hydrogen sulphide be present; if 
the gas be in solution it will immediately blacken upon the 
addition of a soluble salt of lead. In each case the dark 
color is due to the formation of lead sulphide. The converse 
of course holds, and the presence of lead in solution may be 
detected by the addition of hydrogen sulphide or any soluble 
sulphide. 

Preparation of Hydrogen Sulphide. It may be prepared 
by the direct union of its elements but for laboratory pur- 
poses it is generally obtained by the action of sulphuric or 
hydrochloric acid upon iron monosulphide, 

2HCl+FeS=FeCl 2 +H 2 S; H 2 S0 4 +FeS=FeSO,-fH 2 S. 

The gas is given off without the application of heat. 
Obtained in this way the hydrogen sulphide nearly always 
contains hydrogen due to the presence of free iron in the 
iron sulphide. 

The pure gas may be prepared by heating antimony sul- 
phide with hydrochloric acid, Sb 2 S3+6HCl=2SbCl s +3H a S; 
in this method hydrochloric acid must be used for dilute 
sulphuric acid scarcely acts upon the antimony sulphide and 



140 

the concentrated decomposes the hydrogen sulphide liber- 
ated. 

The salts of hydrogen sulphide form an important class 
of ores of the useful metals and their properties will be sub- 
sequently described. 

COMPOUNDS OF SULPHUR AND OXYGEN. 

Four oxides of sulphur are known — the dioxide, S0 2 ; the sesquiox- 
ide, S 2 3 ; the trioxide, S0 3 ; and the persulphuric oxide, S 2 7 . The 
first two are important, the last two are scarcely known in the sep- 
arate state and will not be described. 

SULPHUR DIOXIDE; S0 2 . 

Occurrence. Sulphur dioxide occurs in the gaseous eman- 
ations from volcanoes and has been detected in the waters of 
certain volcanic springs. It is sometimes present in the air 
of towns or in the neighborhood of manufacturing works, in 
these cases resulting from the combustion of the sulphur of 
the fuel or by liberation in some chemical process. It has 
already been stated that sulphur dioxide is always the pro- 
duct of the combustion of sulphur in air or oxygen. It is 
removed from the air by oxidation and converted into sul- 
phuric acid. 

Physical and Chemical Properties of Sulphur Dioxide. 

It is liquefied at ordinary temperature under two atmospheres 
of pressure. Its boiling point is- -8° C. and it produces great 
cold by its evaporation. Water dissolves about 40 times its 
volume at ordinary temperature and the solution is believed 
to contain sulphurous acid but the acid has not been obtained 
in the separate state. Its formula shows it to be over twice 
as heavy as air. It extinguishes flame and is sometimes used 
to extinguish burning soot in a chimney, the sulphur being 
burned in the fire-place. It is a stable compound and not 
readily decomposed; at a high temperature it will combine 
with oxygen passing to sulphur trioxide. It is poisonous, 
causing death very quickly when breathed in a pure state 
and being injurious in even small quantity. 



141 

Preparation and Uses. In the laboratory sulphur dioxide 
is generally prepared by deoxidizing" sulphuric acid by heat- 
ing" with copper or carbon, 

2H 2 S04+Cu=CuS0 4 +2H 2 0+S0 2 ; 2H 2 S0 4 +C = C0 2 +2H 2 
-f2S0 2 ; the first is the more convenient method for all 
ordinary illustration. 

As a general rule it may be stated that those metals which 
act upon sulphuric acid at common temperature liberate 
hydrogen while those which act only by elevating the tem- 
perature liberate sulphur dioxide. Owing to its great specific 
gravity the gas may be collected by displacement or may be 
collected over mercury. 

USES OF SULPHUK DIOXIDE. 

Sulphur dioxide is extensively used as a bleaching agent 
for wool and straw goods which would be injured by chlorine. 
The presence of water is necessary for the action conse- 
quently the goods are usually moistened and subjected to the 
action of the gas. The sulphurous acid in bleaching often 
appears not to destroy the coloring matter but to form color- 
less compounds with it, for the original color frequently 
returns after the lapse of time. In other cases the action 
appears to be due to the abstraction of oxygen from the dye 
leaving it colorless. 

The solution of the gas in water is found to possess great 
deoxidizing power and it is thought to be due to the reaction 
between the sulphur dioxide and water by which hydrogen is 
liberated, the liberated hydrogen then abstracting the oxygen 
from the other body. 

Sulphur dioxide still further resembles chlorine in that it 
is used as a disinfectant. Clothes and buildings are often 
fumigated by burning sulphur but its action in this respect 
has been over-estimated. It has also been used as an anti- 
septic or preservative as it prevents and stop* fermentation. 
Wine and beer casks are sometimes treated with it to prevent 



142 

change in the fresh liquor introduced, and certain salts of 

sulphurous acid may be used for the same purpose. 

Sulphurous Acid and Sulphites. The solution of sulphur dioxide in 
water is believed to contain sulphurous acid H 2 S0 3 . This compound 
is not known in a free state but a large number of salts is known 
which can be obtained by treating the gaseous solution in water with 
bases. This fact justifies the conclusion that the acid exists and its 
salts indicate the formula H 2 S0 3 . The acid characters of the com- 
pound are not strong and it is very unstable, soon passing to sul- 
phuric acid. The salts are of course called sulphites and as the acid is 
bibasic there are two kinds. Sodium sulphite is largely used in the 
manufacture of paper, to destroy the excess of chjorine used in the 
bleaching. 

Sulphur Trioxide, Sulphuric Oxide, Sulphuric Anhydride, S0 3 . The 

compound may be formed by the direct union of sulphur dioxide and 
oxygen, by passing a mixture of the gases through a tube containing 
finely divided platinum. It may also be obtained by gently heating 
fuming sulphuric acid as indicated by the equation, H 2 S 2 7 (heated)= 
H 2 S0 4 +S0 3 . 

Pure sulphur trioxide is a liquid at ordinary temperature. It 
crystallizes when cooled in long transparent prisms which melt at 14.8° 
C. It fumes in the air and the solid form soon deliquesces. The oxide 
combines violently with water forming sulphuric acid. A piece of the 
solid oxide dropped into water hisses similarly to a red-hot iron. It is 
decomposed by heat into sulphur dioxide and oxygen. 

SULPHURIC ACID; H 2 S0 4 . 

Sulphuric acid is of fundamental importance both in the 
arts and sciences and, in fact, is the most important and 
useful acid known. It is a principal agent in the preparation 
of inorganic acids described already and of nearly all other 
acids. In a great majority of the arts and trades, sulphuric 
acid finds a greater or less application. The variety and 
extent of the demand for this acid makes its manufacture 
one of the most extensive and important of modern indus- 
tries. Owing to the above facts theory and practice combine 
to perfect the process of its manufacture which has now 
reached a high state of perfection. 

The other important inorganic acids are obtained from 
their salts but this one is mainly made from its elements — 



143 

built up from its constituents. The constituent raw materials 
most abundantly required in the manufacture are sulphur, 
oxygen, and water vapor the last two being" essentially 
without cost. 

The Leaden Chamber Process. The principal process 
employed depends upon the fact that sulphur dioxide in the 
presence of water vapor and certain oxides of nitrogen and 
the oxygen of the air, is converted into sulphuric acid. The 
fundamental reaction results may be expressed as follows — 
3S0 2 +2HN03+2H 2 0=3H 2 S0 4 H-2NO; 2NO+0 2 =2N0 2 ; 2N0 2 
+2S0 2 +2H 2 0=2H 2 S0 4 +2NO— the last two operations are 
continually repeated. 

It appears that the nitric oxide acts as a carrier of oxygen 
taking it from the air and becoming nitric peroxide. By 
transfer of oxygen to the sulphuric acid the peroxide is 
reduced to nitric oxide and the operation is repeated con- 
tinuously. If no loss of the nitrogen oxides occurred, a 
given quantity of nitric oxide would suffice to convert an 
indefinite amount of sulphurous acid gas into sulphuric acid 
but owing to unavoidable loss, it is necessary to constantly 
replenish this compound. This is usually done by generat- 
ing a small quantity of nitric acid by the action of sulphuric 
acid upon sodium nitrate and the nitric oxide is produced as 
in the first of the above reactions. 

The process of manufacture is as follows — Sulphur or 
metallic sulphides are burned in the air to produce sulphur 
dioxide. A small amount of the vapor of nitric acid is 
produced by the action of sulphuric acid upon sodium nitrate 
which vapor is caused to mingle with the sulphur dioxide 
and the oxygen of the air. To this mixture of gases in 
suitable apartments is added the proper amount of steam, 
when the reactions above indicated take place. 

The plant employed in the process consists of 1st. The burner, in 
which tho sulphur or sulphides are burned for the production of the 
sulphur dioxide. Through those burners is also admitted the air to 



144 

supply the oxygen required for the formation of the vitriol. 2nd, The 
arrangments employed for the production and introduction of the 
nitric acid vapor. These differ but that most generally used consists 
of a series of earthen ware or iron pots which are placed in the "nitre 
oven " ; these pots receive the charge of sulphuric acid and nitre for the 
production of nitric acid. The " nitre oven" is usually a sort of receptacle 
in some part of the burner or its flues so that the heat from the burner 
promotes the evolution of the nitric acid and the vapor of the acid is 
carried along with the air and sulphur dioxide. 3rd, The chambers 
which are immense rooms completely lined with sheet lead. They vary 
in number and size, usually however there are three or four with a 
capacity of from 40000 to 80000 cubic feet each. Into these chambers the 
gases from the burners are introduced and at various points jets of 
steam are projected into them. The floors of the chambers are soon 
covered with a solution of sulphuric acid. 4th, In addition to the 
above mentioned parts of the plant there are supplementary appliances 
generally used, the most important of which are two towers. One sit- 
uated between the burners and the chambers and the other at the exit 
end of the last chamber. The tower at the exit end of the chambers is 
to prevent the waste of the oxides of nitrogen, while the nitrogen of 
the air which takes no part in the chemical action in the chambers, is 
being removed therefrom. This exit called Gay Lussac's tower, is a 
tall chamber filled with porous material over which oil of vitriol is 
allowed to flow. The useless nitrogen escapes from the tower by a flue 
leading from the top of the tower to the chimney stack of the works 
but the oxides of nitrogen are absorbed by the oil of vitriol. The acid 
from this tower is pumped ufj and caused to descend over acid proof 
brick in another toAver (Glover's), which is placed between the burners 
and the chambers. The hot gases from the burners also pass through 
Glover's tower and in so doing they take up the oxides of nitrogen 
from the "nitrous" vitriol and return them to the chamber. The hot 
gases from the burners in passing through Glover's tower also carry 
back steam into the chambers and thus save fuel in steam raising. In 
the Glover towers the production of sulphuric acid takes place to a 
greater extent than in any other part of the chambers of the same 
cubical contents. The towers are not in universal use but they accom- 
plish great economy in the manufacture. When a Glover tower is used 
the whole of the chamber acid, as well as that from the Gay-Lussac 
tower, may be passed through it; the chamber acid is thus concen- 
trated by the heat of the gases from the burners and the gases are 
themselves cooled to the required temperature. 

If the chamber acid is passed through the Glover tower it has a 
specific gravity about 1.72 and is strong enough for many rough chemi- 
cal manufactures. If the chamber acid is not sent through the Glover 
tower, it is taken from the chambers when it reaches the specific 



145 

gravity about 1.60, for it then begins to absorb the oxides of nitrogen. 
This acid is strong enough for some applications but is usually further- 
strengthened by heating in leaden pans until it reaches a specific 
gravity about 1.72. 

The concentration can not be carried further in leaden pans because 
of the action of the acid upon the lead. 

The acid of specific gravity of 1.72 contains about 80 parts of sul- 
phuric acid and for greater strength the evaporation is carried on in 
glass, platinum or iron stills and this is the most expensive part of the 
operation. The concentrated acid of commerce thus obtained contains 
98 parts of sulphuric acid and has a specific gravity of 1.84. The com- 
mercial acid generally contains some impurities, the most common of 
which are iron sulphate, lead sulphate, oxides of nitrogen, and arsenic. 
The last two may be removed by proper treatment and the first two 
by the actual distillation of the acid. 

At a distance from the factories the cost of the acid is largely increased 
because of the risk involved in the transportation. In case of breakage 
or leakage in transportation it is a very difficult body to manage. 

Pyrites now supplies the sulphur for much the larger pro- 
portion of sulphuric acid. In America the greater portion 
of the sulphur is from native sulphur, but the pyrites 
industry is constantly growing. The United States now pro- 
duces annually about 750,000 tons of sulphuric acid. The 
greatest uses of the acid in this country are in the phos- 
phate industries and in the refining of petroleum and manu- 
facture of high explosives.* 

*Mr. W.K. Quinan, Superintendent of the California Powder Works, 
informs the writer that certain advantageous improvements have 
recently been introduced in this country in acid manufacture. When 
pyrites is used as a source of sulphur it is almost impossible to obtain 
a perfectly clear acid, but by the improvements just referred to certain 
works have succeeded in producing a "sales" acid of 96 per cent 
strength in the Glover tower. This is done by lining the tower with 
very refractory material and greatly raising the temperature of the 
tower by conserving the heat from the burners. From the same 
authority it is learned that certain of the American works have 
succeeded in producing an artificial draught through the chambers by 
means of rotating fans placed in the flue at the end of the chamber 
system. This plan was first tried in Germany, but did not succeed 
then. This permits the production of a much greater amount of acid 
in the same chamber space. The acid chambers attached to the works 
above referred to yield three pounds of concentrated B 2 S0 4 to each 
pound of sulphur burned. 
10 



146 

Physical and Chemical Properties of the Acid. The 

concentrated acid obtained by the processes described 
always contains from one to two per cent of water. All 
the weaker acids by evaporation finally attain this composi- 
tion and then distil over unchanged at the temperature of 
338° C. The vapor evolved during the distillation is not that 
of sulphuric acid but is a mixture of sulphur trioxide and 
water vapor which pass over and condense together in the 
receiver. If pure, the acid is a colorless, heavy, oily liquid. 

The acid has a powerful affinity for water and readily 
absorbs moisture from the atmosphere ; for this reason it is 
often used as a dessicating agent. It is thus employed in 
the laboratory for drying without heat. The objects to be 
dried are placed over a dish of sulphuric acid in a closed 
vessel and the operation is greatly facilitated by exhausting 
the air from the vessel. The acid is also frequently used to 
dry gases, the gases being made to pass over a surface of the 
acid. Pumice stone soaked in the acid is admirably adapted 
to exposing the gases to the action. 

The acid combines energetically with water, so that 
caution is always necessary in mixing them — the acid should 
always be poured into the water and not the reverse. The 
temperature produced by mixing the acid and water often 
exceeds that of boiling water. If four parts of the acid be 
added to one of powdered ice or snow there is an elevation 
of temperature, but if the proportions be reversed there is a 
reduction of temperature. 

Owing to its affinity for water it decomposes many 
organic compounds containing hydrogen and oxygen, remov- 
ing from the bodies these elements in the proportions to 
form water; it thus acts upon alcohol and oxalic acid. In a 
similar manner it acts upon paper, wood and sugar, remov- 
ing the oxygen and the hydrogen in the proportion to form 
water and leaving the carbon in excess, with the result of 
charring the body. This action is finely illustrated in the 



147 

case of sugar as follows: Dissolve some crystalline cane 
sugar in three-fourths its weight of warm water and allow it 
to partially cool; then add a volume of concentrated acid 
equal to two-thirds of the volume of the water used, the 
liquid blackens and froths up as a spongy mass of carbon. 
Even when much diluted the acid corrodes and destroys 
textile fabrics. 

Under the influence of heat it decomposes the salts of all 
acids more volatile than itself. On this account the acid is 
often said to be the strongest of the mineral acids, but this 
ability to decompose the salts of other acids is not alone the 
test of the strength of an acid as has already been pointed 
out. 

At a red heat the vapor of the acid is decomposed accord- 
ing to the following reaction, H 2 S0 4 (heated) = S0 2 +H 2 0-fO. 

Acids corresponding to the formula H 2 S0 4 of 100 per cent purity 
can be obtained by adding to the concentrated acid the exact amount 
of sulphur trioxide to combine with the water there present. When 
the concentrated acid containing 97 or 98 per cent of sulphuric acid is 
cooled to — 10° C. or below that point, the pure acid crystallizes and 
may be separated in the pure state; the latter process is now carried 
on upon a manufacturing scale. 

In combining with water the acid forms several definite compounds 
the best known of which are the combinations resulting from the union 
of one molecule of acid with one or two molecules of water which may 
be respectively represented by the formula? H 2 S0 4 ,H 2 and H 2 S0 4 , 
2H 2 0. 

SULPHATES. 

Sulphuric acid acts readily upon metallic oxides and 
carbonates converting them into sulphates in the latter case 
with the evolution of carbon dioxide. Sulphuric acid cold or 
hot, dissolves all the metals except gold and platinum. The 
boiling acid attacks silver forming the sulphate with evolu- 
tion of sulphur dioxide. Under the same conditions it also 
acts slightly upon platinum. The very strong acid does 
not act upon cast iron. This metal can therefore be used for 
concentrating the acid after it reaches the strength which 



148 

attacks platinum. Before it reaches this strength it acts 
more readily upon iron than platinum. In the California 
powder works the last concentration takes place in iron 
retort, and Mr. Quinan states that chilled cast iron offers a 
high degree of resistance even to weaker acid. Gold is not 
acted upon hence the acid is often used in separating gold 
and silver or parting these metals. Generally speaking 
those metals which are acted upon at ordinary temperature 
by dilute acid liberate hydrogen, but when the concentrated 
acid or elevated temperature is required the corresponding 
sulphate is usually formed with the liberation of sulphur 
dioxide. This latter result is probably due to the decom- 
position of the strong acid by the liberated hydrogen, 
especially at high temperature. 

The sulphates are an important class of compounds many 
of them being extensively employed in the arts. They are 
insoluble in alcohol; as a class they are soluble in water 
except those of lead and of the alkaline earth metals 
(calcium, strontium, and barium), and these are slightly 
soluble except that of barium which is absolutely insoluble 
in water and only slightly so in acids. The normal sulphates 
are decomposed by heat except those of the alkali and 
alkaline earth metals and of magnesium, the latter only 
partially decomposing at very high temperature. The 
insolubility of the barium sulphate gives a ready preliminary 
test for the detection of any sulphate in solution — which is to 
add to the suspected solution any soluble salt of barium and 
if any sulphate be present a white precipitate will be formed 
insoluble in water and dilute acid. 

Pyro-sulphuric Acid or Di-sulphuric Acid. This acid is 
also called fuming sulphuric acid, Nordhausen oil of vitriol. 
Its formula is H2S2O7 (H 2 S0 4 , S0 3 ). It may be considered as 
consisting of a molecule of sulphuric acid and one of sulphur 
trioxide or two molecules of sulphuric acid less one of water. 
It is now made on a manufacturing scale by dissolving- 



149 

sulphur trioxide in sulphuric acid. This acid was originally 
manufactured at Nordhausen in Saxony, a fact which ex- 
plains one of its names. The original method consisted in 
distilling the basic ferric sulphate of iron by which sulphur 
trioxide was evolved and condensed in a solution of sul- 
phuric acid. The basic salt being obtained by oxidizing 
ferrous sulphate by exposing it to a moderate heat in air. 
This acid fumes in the air when the bottle containing it is 
open, due to the escape of sulphur trioxide. It is heavier than 
the common acid, its specific gravity being 1.9. It has important 
application in the preparation of indigo dyes and in the colors 
obtained from coal tar. This acid was obtained by the last of 
the above processes as early as the fifteenth century. 

Thiosulphuric Acid; H 2 S 2 3 . It was formerly called hyposulphuric 
acid. This acid has not been obtained in a free state being very 
unstable. 

Its salts however are stable and numerous, by far the most import- 
ant being the sodium thiosulphate. This salt is simply prepared by 
digesting powdered roll sulphur with solution of sodium sulphite 
(Na 2 S0 3 ). The latter salt combines with an atom of sulphur forming 
the thiosulphate (Na, 2 S 2 3 ) which maybe crystallized from the solu- 
tion. This is the salt so largely used in photography and commonly 
called hyposulphite or "hypo." It is also used as a substitute for 
sodium sulphite as an antichlore. The acid may be regarded as obtained 
from sulphuric acid by replacing one atom of oxygen by an atom of 
sulphur— hence the old term hyposulphurous is not strictly applicable. 

Hyposulphurous Acid; (H 2 S 2 4 ). The solution of this acid has 
been obtained but it rapidly decomposes. Its salts are more stable 
than the acid. The sodium salt is the most important and is obtained 
by the action of zinc filings upon a concentrated solution of the acid 
sodium sulphite. This salt is used by the dyer and the calico printer 
and its formula appears to be Na 2 S 2 4 . 

There are several other oxy-acids of sulphur whose names and 
formulae are here given, dithionic, H 2 S 2 6 ; trithionic, H 2 S 3 0, ; ; tetrath- 
ionic, H 2 S 4 6 ; pentathionic, H 2 S 5 6 ; very little is known of these and 
they are of little practical importance. 

SELENIUn AND TELLURIUH. 
Selenium. It is a rare element and much resembles sulphur in its 
mode of occurrence, physical and chemical properties. It lias been 
found in the free state but in very small quantity associated with sul- 
phur. It usually occurs as selenides of the metals together with the 



150 

sulphides. Selenium has been obtained in several allotropic forms the 
most distinct of which are the varieties which are soluble and insoluble 
in carbon disulphide. 

The crystalline form of selenium is a conductor of electricity and 
this power is much greater in light than in darkness. This alteration 
of conducting power with variation of light intensity has been made 
use of in constructing the photophone but the instrument has not yet 
proved of practical value. The name Selenium is from the Greek word 
(Sefarjvri) for moon, the closely resembling element having been called 
tellurium from tellus the earth. 

Tellurium. Tellurium is even less common than selenium. It has 
been found native in some gold ores, and in combination with gold and 
some other metals. It has recently been found in masses of 20 pounds 
weight in Colorado. It has the external appearance and lustre of 
bismuth and in its physical properties more closely resembles the metals 
than non-metals. In its chemical relations it is closely related to selen- 
ium and both these elements are connected by strong analogies with 
sulphur. Both tellurium and selenium form oxides and oxy-acids 
analogous to sulphurous and sulphuric oxides and the corresponding 
acids. They also form hydracids analogous to hydrogen sulphide, 
each of the above elements replacing sulphur in the respective com- 
pounds. Tellurium and selenium likewise combine with the chlorine 
group and notwithstanding their similarity to sulphur they both form 
sulphides. 

PHOSPHORUS; P. 

Occurrence. Phosphorus is very widely though not 
abundantly distributed in its compounds, but it never occurs 
in a free state. It is an essential constituent of all fertile 
soils. It is necessary to the growth of certain parts of the 
vegetable structures, especially of fruits and seeds. From 
plants used as food the compounds of phosphorus pass into 
the animal body and are essential constituents of the juices 
of the animal tissue, and more especially of the bony skel- 
etons of animals which contain nearly three-fifths their 
weight of calcium phosphate. Its compounds are found 
in all sea water, generally in river water, and in many 
springs. It has also been found in meteoric stones. Phos- 
phorus accordingly ranks with carbon, hydrogen, oxygen, 
and nitrogen as one of the elements essential to organic life. 
This element was discovered by Brand in 1668 ; he obtained 



151 

it from urine. Between 1670 and 1680 it is said to have been 
exhibited to several crowned heads of Europe as one of the 
wonders of nature. (Roscoe and Schorlemme, Treatise on 
Chemistry, vol. 1.) 

Preparation of Phosphorus. Formerly phosphorus was 
entirely obtained from bone-ash, but now the greater cheap- 
ness of many of the phosphates of mineral origin has led to 
their use for the manufacture of phosphorus. Other things 
being equal bone-ash is still the most desirable raw material 
for obtaining phosphorus; the ash is tricalcic diphosphate 
Ca 3 (P0 4 ),. 

The essential chemical principles involved in the prepara- 
tion of phosphorus may be stated as follows: The calcic 
phosphate is treated with sulphuric acid, which liberates the 
tribasic phosphoric acid with production of calcium sulphate. 
The tribasic acid under the application of heat loses 
water and becomes the monobasic acid. This acid is deoxi- 
dized by carbon with the liberation of phosphorus and 
formation of carbon monoxide. The changes are indicated 
by the reactions, Ca 3 (P0 4 )2+3H 2 S0 4 =3CaS0 4 +2H 3 P(V, by 
drying at low red heat, HsPO^HPOs+IiO; 2HP0 3 +6C= 
6CO+H 2 +P 2 . 

The mechanical steps of manufacture may be outlined as follows — 
finely powdered bone-ash or other tricalcic phosphate is treated with 
sulphuric acid; the calcium sulphate thus produced is separated by 
filtration from the acid liquor, which contains orthophosphoric acid. 
This liquor is concentrated by evaporation in leaden pans. It is then 
absorbed by powdered charcoal, coke, or sawdust and heated to a dull 
red heat, by which action the orthophosphoric acid (H 3 P0 4 ) is con- 
verted into meta-phosphoric acid (HP0 3 ). The mixture of meta- 
phosphoric acid and carbon is now distilled in clay retorts, when the 
phosphorus is separated and condensed under water which soon 
becomes warm and in which the melted phosphorus is conveyed to 
certain points from which it is removed. 

Note.— By some authorities it is held that all the calcium is not 
removed by the sulphuric acid from the tricalcic phosphate but that 
the acid phosphate CaH 4 (P0 4 ) 2 is formed which is dissolved in the 
acid. liquid and converted into the metaphosphate of calcium by heat- 



152 

ing with carbon. This inetaphosphate then liberates phosphorus 
when distilled with carbon. 

The crude phosphorus thus obtained is purified by 

fusion and solidification and finally cast into sticks or wedges 

the entire operation being conducted beneath the surface of 

warm water. With unimportant exceptions the entire 

supply of the world's phosphorus is made at two places, 

Birmingham, England, and Lyons, France. To a small 

extent phosphorus has been produced in Philadelphia, 

Sweden and Russia. 

Properties of Ordinary Phosphorus. Ordinary phospho- 
rus when freshly made as above described is a translucent 
almost colorless wax-like solid. At ordinary temperature it 
is somewhat harder than wax, is flexible and sectile; at 5.5° C. 
and below, it becomes hard and brittle. Even in the dark it 
soon loses its translucency and becomes coated with an 
opaque white film. This action is hastened by the light, and 
by the action of direct sunlight it becomes red due to the con- 
version into the allotropic red phosphorus. It melts at 44° C. 
It is insoluble in water and usually kept immersed in that 
liquid. It is soluble in naphtha and carbon disulphide. It 
crystallizes when deposited from solution in carbon disul- 
phide. Its specific gravity is 1.83 at 10° C. 

Exposed to the air phosphorus gives off fumes and glows 
with a faint greenish light; both these phenomena are 
believed to be due to the oxidation of the phosphorus, but 
are not thoroughly understood. 

It inflames in the air when heated above its melting tem- 
perature and burns with a brilliant white flame evolving 
white clouds of P 2 5 . In pure oxygen this combustion is 
immensely luminous. 

The low temperature of the ignition of phosphorus renders 
great care necessary in handling it to avoid accident. It 
should generally be manipulated under water. Ordinary 
phosphorus is very poisonous when taken internally. The 



153 

vapor is also poisonous when inhaled. Persons engaged in 
manufactures requiring the manipulation of phosphorus are 
often affected by phosphorus poison, very frequently result- 
ing in the decay of the bones, especially those of the jaws 
and nose. 

Phosphorus when moist will combine with oxygen, chlo- 
rine, bromine, iodine, sulphur, and with many of the metals. 

Amorphous or Red Phosphorus. This is the principal 
allotropic form of ordinary phosphorus. When ordinary 
phosphorus is heated for 49 or 50 hours to 230°, or 240° C. in 
ovens, or in an atmosphere that does not act upon it, it is 
converted into a red opaque mass, which is widely different 
from common phosphorus. It is infusible at temperatures 
below red heat, is insoluble in carbon disulphide, is not 
poisonous, emits no vapor, and does not phosphoresce. It 
can not be inflamed by friction and does not even ignite in 
the air when heated to 260° C. at which temperature it is 
reconverted into ordinary phosphorus. The red phosphorus 
is much less chemically active than the ordinary phosphorus. 
This difference of action can be strikingly shown by placing 
the two varieties in contact with iodine when the red is unaf- 
fected and the common phosphorus unites with the iodine 
producing combustion. In the allotropic transformation 
there is no change of weight though the two varieties differ 
in specific gravity. The specific gravity of ordinary phos- 
phorus is about 1.83, that of the red phosphorus is 2.14. 

There are known other modifications of phosphorus. One form 
known as crystallized or metallic phosphorus can be obtained by heat- 
ing- red phosphorus in a sealed tube to 530° C. or common phosphorus 
may be heated to redness in a closed tube with lead for several hours. 
On cooling- the melted lead the phosphorus crystallizes out in black 
scaly crystals. This form is more inactive than the red phosphorus. 
Professor Ilemsen describes a snow-white phosphorus obtained in the 
form of powder by cooling- the vapor of phosphorus by ice- water in an 
atmosphere of hydrogen. The vapor density of phosphorus is i\-2 so 
that its molecule contains four atoms. At very high temperature the 
vapor density diminishes showing- a tendency to correspond to the 
ordinary law of volumes. 



154 

Uses of Phosphorus. The principal use of phosphorus 
is in the manufacture of matches. It is also used to a small 
extent in the preparation of certain vermin poisons. The 
lucifer matches are made by tipping the splints with sulphur, 
wax, or paramne, to surely convey the flame to the wood. 
The match composition consists of phosphorus and some 
oxidizing agent; those most commonly used being potassium 
chlorate, red lead, and lead nitrate. This mixture is usually 
bound together and attached to the wood by glue or gum. 

The safety matches which can not readily be ignited by 
ordinary friction have no phosphorus on the match but are 
coated with a mixture of antimony sulphide and one or more 
oxidizing agents. For ignition the matches have to be 
rubbed on a prepared surface (usually the side of the box 
which is covered with a mixture containing red phosphorus ; 
the red phosphorus mixed with fine sand or powdered glass) . 

Oxides and Oxyacids of Phosphorus. Four oxides of phosphorus 
are known the formulae of which are — P 2 4 , P 2 5 , P 4 6 , and P 4 0. 
The most important of these is the P 2 5 phosphoric oxide. 

Phosphoric Oxide. This oxide is prepared by burning phosphorus 
in dry air. It constitutes the white fumes which are seen when phos- 
phorus burns with flame in dry air. It has a great affinity for water 
and soon deliquesces if left exposed to the air. It is sometimes used as 
a dehydrating agent in the laboratory. It will even extract water 
from oil of vitriol. 

Orthophosphoric Acid; H 3 P0 4 . This is the compound usually 
designated as phosphoric acid. It is the acid whose salts are usually 
met with in nature as phosphates. The phosphates are indispensable 
to the growth and sustenance of plants and animals. In these com- 
pounds phosphorus is widely distributed. 

The acid is the final product of the oxidation of phosphorus in the 
presence of water. It may be prepared by boiling phosphorus with 
nitric acid. It can also be prepared from the native phosphates. The 
acid is tribasic. It was formerly used to a considerable extent in calico 
printing. 

There are several other oxy-acids of phosphorus whose names and 
formulae are given in the following table — 

Hypo-phosphoric acid, H 3 P0 2 ; 
Phosphorous acid, H 3 P0 3 ; 

Meta-phosphoric acid, HP0 3 ; 
Pyro-phosphoric acid, H 4 P 2 7 . 



155 

Other Compounds of Phosphorus. Phosphorus does not combine 
directly with hydrogen but there are three compounds of these two 
elements known. The most important of these is the gaseous phos- 
phuretted hydrogen, phosphine H 3 P. This gas can be prepared in 
several ways and will generally take fire spontaneously when exposed 
to the air but this action appears to be due to the presence of the liquid 
phosphide H 4 P 2 which is spontaneously inflammable. The other 
phosphide H 2 P 4 is a yellow solid. 

Phosphorus combines with the halogens forming two analogous 
compounds of each of the elements, chlorine, bromine, and fluorine. It 
also forms two compounds with iodine, but one of these is without an 
analogue among the other halogen compounds. 

ARSENIC; As. 

Occurrence. Arsenic occurs widely distributed but in small quan- 
tity, and resembles sulphur in its mode of occurrence. It is found 
native but more generally as the sulphides (realgar and orpiment) and 
the arsenides of the metals. It frequently occurs combined with the 
sulphides of the metals. Arsenic is used only to a small extent 
economically. 

Preparation. It is generally prepared in one of two ways. 1. By 
heating arsenical pyrites out of contact with air, the arsenic is distilled 
off and condensed by suitable arrangements. 2. By heating arsenious 
oxide with charcoal, the oxide is reduced and the arsenic is volatilized 
and condensed. 

Properties. In its appearance arsenic resembles a metal. It has a 
steel grey metallic lustre and is a conductor of heat and electricity. Its 
specific gravity is between 5 and 6. It volatilizes without fusing. In 
dry air at ordinary temperature it remains unchanged, but in finely 
divided form it oxidizes in moist air. At a temperature over 70° C. it 
oxidizes in the air and gives off fumes of arsenious oxide accompanied 
by a very penetrating and characteristic odor suggestive of garlic. 
When heated to a red heat in the air it burns with a bluish white flame, 
in oxygen its flame is very brilliant. It is insoluble in water. Pure 
arsenic does not appear to be poisonous but it may be oxidized after it 
is taken internally and then become a poison. In its chemical proper- 
ties it is closely allied to phosphorus. Arsenic forms no base with 
oxygen and hence differs from the elements classed as metals. It is used 
in small quantities to form alloys which possess characteristic proper- 
ties; it is thus used in the manufacture of shot, in bronzing brass and 
in other alloys. 

OXIDES. 

Arsenic forms two oxides, As 4 O e and As,0 5 . 

Arsenious Oxide; As.,0 (; . This compound is prepared on a com- 
mercial scale by roasting arseniferous minerals in suitable furnaces or 



156 

ovens when arsenious oxide is the principal product ; arsenical pyrites is 
usually the ore from which it is obtained. The sulphur and arsenic are 
thus oxidized the former escaping as sulphur dioxide. The arsenious 
oxide generally designated as " arsenical soot" is conducted into cham- 
bers which expose a large condensing surface. The oxide is here con- 
densed to a dark grey powder. 

The workmen employed to clear the chambers are clad in leather 
garments with glazed apertures for the eyes and they breathe through 
wet cloths. The powder is purified by resublimation and then obtained 
as a white, glistening, crystalline powder. If the crystalline arsenic be 
sublimed under slight pressure at high temperature white, amorphous, 
vitreous arsenic is obtained. 

Arsenious oxide is obtained in large quantity as a bye product in 
working up certain volatile ores, mainly those of cobalt, nickel, silver, 
and tin. It is obtained in large quantities in connection with the tin 
furnaces of Cornwall and Devon. 

The substance commonly known as arsenic in the shops is this 
oxide. It is usually sold in the form of a white powder resembling 
flour in appearance but much heavier its specific gravity being 3.7. It 
volatilizes without fusing. It may be distinguished from any resem- 
bling substance by the garlic odor emitted when dropped upon glow- 
ing coal. This odor is thought to be due to a lower oxide. 

Arsenious oxide is a powerful poison, less than three grains have 
proven fatal. The habitual use of it in continually increasing quan- 
tities will enable the system to withstand much larger doses. 

The best antidote for arsenic poison as given in the U. S. pharma- 
copoeia, is a mixture of dilute solution of ferric sulphate and magnesia. 
Carbonate of soda may replace the magnesia and a solution of the 
perchloride of iron may replace the sulphate. Emetics should also be 
used as promptly as possible. This antidote was discovered by 
Bunsen in 1834. It was a deduction from known chemical facts. Previ- 
ous to that time no antidote for this poison was known. 

Arsenious oxide has many applications some of which will be men- 
tioned. 

Uses. It is used medicinally to a certain extent. It is sometimes 
administered to horses to render their coats smoother. It is used in 
calico printing and in the preparation of certain colors, arsenic being 
present in many pigments. It is used in the preparation of aniline, 
in glass making, as a constituent of white fire in pyrotechnics, as a 
preservative of skins, and in the preparation of various kinds of vermin 
poison. 

Arsenious Acid. The acid has not been obtained in a free state. 
The solution of arsenious oxide in water, however, yields precipitates 
with certain metallic salts which indicate that the acid is tribasic, 
H 3 As0 3 . The brilliant Scheele's green is the arsenite of copper 



157 

(CiiHAs0 3 ). The arsenites are insoluble or difficultly soluble in water, 
except those of the alkalies. The formulae of the alkaline arsenites 
indicate that they are derived from HAs0 2 . Fowler's solution used in 
medicine is the arsenite of potassium. 

Arsenic Oxide and Acid. This oxide can be obtained by heating 1 
arsenic acid. The acid is prepared by oxidizing As 2 3 with nitric acid 
under proper precautions. 

This acid is largely used as a substitute for tartaric acid in calico 
printing and in the preparation from aniline of rosaniline or the mag- 
nificent magenta dye. 

Arsenetted Hydrogen ; H 3 As. This is the only compound of arsenic 
and hydrogen known. It is always formed when nascent hydro- 
gen and arsenious oxide are brought together in acid solutions. It 
is of importance because its production affords a means of detecting 
the presence of a very minute quantity of arsenious oxide. Marsh's 
test for detecting arsenic in cases of poisoning depends upon the pro- 
duction of the gas. The gas itself is exceedingly poisonous and any 
experiment with it should be undertaken with very great care. The 
chemist Gehlen lost his life by inhaling the gas. 

Sulphides of Arsenic. There are known three sulphides of arsenic, 
the disulphide As 2 S 2 , the trisulphide As 2 S 3 , and the penta-sulphide 
As 2 S 5 . The two first named occur native. 

As 2 S 2 , Realgar. This compound occurs native crystallized in red 
rhombic prisms. It may be prepared by heating arsenic with sulphur, 
or arsenious oxide with sulphur. The. form which occurs in nature 
under the name of realgar, red orpiment, is usually prepared by 
distilling iron pyrites and arsenical pyrites together when the realgar 
distils over. It is used in the manufacture of the Bengal signal lights 
and Indian fire. In the air it burns with a blue flame ; with nitre it 
gives a brilliant white light. 

The Bengal lights are composed of a mixture of 24 parts of potas- 
sium nitrate, 7 of sulphur, and 2 of realgar. 

As 2 S 3 , Yellow Orpiment. This compound occurs native crystallized 
in yellow rhombic prisms. It may be prepared by heating arsenic with 
the proper amount of sulphur. 

The paint known as King's yellow is a mixture of yellow orpiment 
and arsenious acid and is of course poisonous. 

The penta-sulphide is of less importance than the other two. 

Compounds of Arsenic with the Halogens. Arsenic forms but one 

chloride, the trichloride AsCl 3 . It forms analogous compounds with 
bromine, iodine, and fluorine. It also forms a dicarbide. 



158 

ARGON AND HELIUfl. 

Argon. This body was very recently discovered. Lord Rayleigh 
had found that the specific gravity of chemically pure nitrogen was not 
the same as that of the nitrogen of the atmosphere. This led to the 
examination of the atmosphere and to the discovery that it contained 
a substance not previously recognized, amounting to nearly one per 
cent. By the combined efforts of Lord Rayleigh and Professor Ramsey 
the substance was isolated in 1894. The new body was named Argon 
(signifying without work) in allusion to its chemical inactivity. The 
investigations up to this time indicate that Argon is an element with 
density of 20, referred to hydrogen. It appears to be mon-atomic and 
hence its atomic weight would be 40. It has been liquefied and solidified 
by great cold and pressure. It has, up to this time, resisted all 
attempts to cause it to combine with other bodies. As there have 
been very extended efforts to form a compound with Argon, with neg- 
ative results, Professor Ramsey thinks that it may be non-valent or 
incapable of forming compounds. 

Helium. The existence of this body has been inferred for a consid- 
erable time, through the existence of a bright line in the solar spec- 
trum, not attributed to any known body. In seeking for a combined 
form of argon, Professor Ramsey for the first time in 1895 identified 
Helium among terrestrial bodies. It has not yet been definitely decided 
whether the body is an element, or a compound, or a mixture. The 
body is gaseous and has resisted all attempts to liquefy it although it 
has been subjected to enormous pressure and to the greatest attain- 
able cold. Its boiling point under atmospheric pressure, according to 
Olszewski, must be below —264° C. Helium, like argon, has resisted all 
attempts to form from it a compound with other elements. 



CHEMISTRY OF THE METALS AND THEIR 

COMPOUNDS. 



THE ALKALI METALS. 

The most important elements of this group are sodium 
and potassium. The other members are lithium, rubidium, 
and caesium. The first two are abundant in nature and 
widely distributed. Lithium is widely distributed, but only 
in small quantity. The last two members of this group are 
still more rare. These elements are highly electro-positive 
and as already stated their hydroxides are powerfully alka- 
line and their salts are generally soluble. The elements are 
soft, silvery white metals all of which decompose water and 
the two last of the group take fire in the air. 

POTASSIUM; K; 39.1. 

Occurrence. Potassium is not found in a pure state in 
nature but it occurs abundantly as a chloride in combination 
with other chlorides forming immense deposits. In combi- 
nation with silicon and aluminum, it is a common constitu- 
ent of the igneous and metamorphic rocks. From these 
rocks, by disintegration, it passes into the soil and finally 
into the plants, of which it is an essential food ingredient. 

From plants the salts of potassium pass into the organ- 
isms of animals. In plants it is mainly present as salts of 
vegetable acids. 

Preparation. Potassium was first isolated by Davy in 
1807, by decomposing the hydroxide by electricity, the potas- 
sium appearing at the negative pole. 



160 

The method of Davy for preparing" potassium has long 
since been superseded. It is now prepared by deoxidizing 
potassium carbonate with charcoal. For a good yield the 
ingredients should be thoroughly mixed. An intimate mix- 
ture of potassium carbonate and charcoal is obtained by cal- 
cining potassium tartrate (C 4 H 5 6 K) in a covered crucible 
and this method is generally followed in preparing the car- 
bonate for deoxidation. 

The mixture of potassium carbonate and carbon is dis- 
tilled in iron retorts from which a short iron pipe leads to a 
receiver containing petroleum and kept cool by ice water. 
When the retort is heated to a high temperature the potas- 
sium distils over and condenses under the petroleum. The 
reaction occurring is indicated by the following equation, 
K 2 C03+C2=K 2 +3CO. The metal thus obtained is not pure 
and has to be redistilled or subjected to other treatment to 
perfectly purify it. 

Metallic sodium is now again being manufactured by elec- 
trolysis and it is probable that Davy's method for obtaining 
potassium by electrolysis may be reintroduced. 

Properties and Uses. Potassium is a silver white metal, 
specific gravity of .865 and rapidly tarnishes when exposed 
to the air. It floats on water and takes fire when placed 
upon water or even upon ice. More properly speaking the 
potassium decomposes the water and the liberated hydrogen 
takes fire, at the same time volatilizing some of the potas- 
sium, which burns with a violet color. Potassium melts 
below the boiling point of water. The greater difficulty 
attending the preparation of potassium and the fact that 
sodium can replace it in industrial operations has almost 
entirely limited its application to laboratory purposes. It 
will be seen from the relative atomic weights of potassium 
and sodium, that for equal weights, the latter element can do 
more chemical work. 



161 

Potassium Carbonate; K 2 C0 3 . This important salt is 
obtained on a commercial scale by several different processes. 
Formerly most of the potash or crude carbonate was obtained 
from wood-ashes, but this source has greatly decreased in 
importance and now only parts of the United States, Canada, 
Russia, Hungary, and Galicia supply it from this source. 
The amount of the carbonate however from wood-ashes is 
greater than that from any other single source. 

Potassium Carbonate from Wood- Ashes. It has already 
been stated that potassium exists in plants as the salts of 
organic acids. When the wood is incinerated the organic 
salts are decomposed and the potassium is left in the form of 
the carbonate. Of course the ashes contain other mineral 
substances resulting from other salts present in the plants. 
By lixiviation with water the more soluble salts are separated 
from the less soluble ; the former consists mainly of potas- 
sium carbonate with considerable portions of potassium 
sulphate and chloride ; the former consist mainly of potassium 
sulphate and chloride. By evaporation a considerable por- 
tion of the sulphate may be removed as it is less soluble than 
the carbonate. The residue then evaporated to dryness and 
calcined gives the crude potash of commerce which contains 
much potassium chloride and some sulphate. When greater 
care is observed in the process the product is purer and 
known under the name of pearlash. 

Potassium Carbonate from Beet-Boot Molasses. In making 
sugar from the beet-root there is left a syrup which can not 
be made to crystallize; this syrup is rich in mineral salts 
especially those of potassium. The syrup is first fermented 
for the production of alcohol. The liquor left behind is, in 
France, called "vinasse" and in G-erman " schlempe." This 
liquor evaporated to dryness, calcined and the cinder lixivia- 
ted furnishes a high percentage of potash salts, lv>CO :; , 
K2SO4, and KOI. This industry has obtained great develop- 
ment in Germany and France, 
11 



162 

Potassium Carbonate from the Chloride. A large amount 
of potassium carbonate is made from the native chloride by 
a process similar to that employed in the manufacture of 
sodium carbonate from common salt, yet to be described. 

Potassium Carbonate from Sheep Wool. The washing 
from sheep wool is called " suint" and contains a considerable 
quantity of potassium mainly combined with animal acids. 
By evaporating the liquid to dryness and burning the residue 
the organic salts are decomposed and the carbonate of potas- 
sium left. This is separated by lixiviation from the ash. 

The potassium carbonate is obtained from other sources 
in small quantity but not on a commercial scale. 

Properties and Uses of Potassium Carbonate. The nor- 
mal potassium carbonate is a white solid extremely deli- 
quescent and soluble in less than its own weight of water, 
yielding a strongly alkaline solution. It is insoluble in 
alcohol. This substance is an important compound being 
used in the manufacture of soap and glass. In many States 
of America the country population make their own soap 
obtaining the potash "from the ashes of the wood used as 
fuel. 

The Acid Carbonate or Bicarbonate of Potassium. It can 

be prepared by passing carbon dioxide through moist potas- 
sium carbonate or through a solution of potassium carbonate. 
The salt is less soluble and less alkaline than the normal salt. 
It is converted into the normal carbonate by heat, 
2KHC0 3 (heated) =K 2 C0 3 +H 2 0+C0 2 . It is used to a small 
extent in medicine. 

Caustic Potash ; KOH. This substance may be prepared 

by adding a solution of slaked lime to a boiling dilute 
solution of potassium carbonate, K 2 C0 3 +Ba6®s=CaC0 3 + Q^oh), 
2KOH ; the reaction will not take place if the solution of the 
carbonate be too strong. The solution decanted from the 
insoluble calcium carbonate and evaporated, leaves a clear 



163 

oily liquid which solidifies to a clear white mass on cooling. 
It is often fused and cast into slabs or sticks. 

The hydroxide is a white solid, can be melted and 
volatilized, but is not decomposable by heat. It is deliques- 
cent and readily absorbs carbon dioxide forming the carbon- 
ate, and is frequently used for removing carbon dioxide from 
gases. It is very soluble in water and evolves much heat in 
dissolving. It is powerfully alkaline being the most power- 
ful alkali in general use. It softens and destroys the skin 
and on this account is used as a cautery. It is one of the 
most useful agents in the laboratory. Near Stayspor t in 
Germany, caustic potassa is now produced in large quantity 
by decomposing a solution of potassium chloride by elec- 
tricity. The works are primarily for the production of 
chlorine and the hydroxide is a valuable by-product. 

Potassium Chloride; KC1. This salt was formerly ob- 
tained as a secondary product in the manufacture of bromine 
from sea water and of iodine from the ash of sea weed, and 
of sugar from beet-roots. It is now almost exclusively 
obtained from the mineral carnallite, which is a double 
chloride of potassium and magnesium, KC1, MgCl 2 , 6H 2 0. 
Carnallite is found in vast quantities overlying the Stassfurth 
salt beds. The chloride is now an important raw material 
for manufacturing potassium carbonate and nitrate. 

Potassium Iodide and Potassium Bromide; KI and KBr. These 
compounds are used to a considerable extent in photography, in medi- 
cine, and in the laboratory. 

They are formed in the same way, by passing bromine or iodine 
into a solution of potassium hydroxide. 

Nitre; Saltpetre; KN0 3 . This important salt is often 
found as an efflorescence upon the surface of the soil in hot 
dry climates. It results from the oxidation of nitrogenous 
organic matter in the presence of potash in the soil. The 
formation of nitre under these circumstances is duo to the 
presence of specific microbes and the nitrification docs 



164 

not take place without them. Nearly all of the native salt- 
petre in commerce comes from the East Indies, one of the 
districts of Bengal supplying the greater portion. It is 
chiefly found in the neighborhood of villages where the 
animal refuse supplies an abundance of organic nitrogen. 
The surface of the soil which shows the white efflorescence is 
scraped off and lixiviated with water. This solution evapo- 
rated to crystallization furnishes "crude nitre" in which 
form it comes into market. 

This native process has been imitated artificially in the 
nitre beds or "saltpetre plantations." In Sweden formerly 
every land owner was obliged to furnish the government 
with a certain quantity of nitre. In France during the Rev- 
olution the artificial production of nitre was compulsory. 

In the artificial process animal and vegetable refuse of various 
kinds are mixed with wood-ashes, calcareous earthy material, old 
mortar, bones, &c. This mass is occasionally moistened with stable 
drainings. After the lapse of the proper time watering is discontinued 
and salts soon effloresce on the surface of the heap. The surface layer 
to the depth of a few inches is then removed and the soluble salts dis- 
solved out. The nitrates found in the solution are those of potassium, 
calcium, magnesium, and ammonium; the last three of which may be 
transformed into potassium nitrate by the addition of potassium car- 
bonate to the solution. 

In this process the basic parts of the nitrates except that of the 
ammonium nitrate, are derived from the earthy matters. The acid 
parts are believed to be formed by the oxidation of the ammonia 
resulting from the decomposition of the organic matter under the 
action of the "nitrifying" microbes. The presence of the bases is very 
favorable to the action. 

Nitre from Chili Saltpetre. By far the greater portion of 
the nitre which now comes into the market, is made from 
sodium nitrate, NaN0 3 , by treatment with potassium chloride. 
Double decomposition ensues in accordance with the reac- 
tion, NaN0 3 +KCl=NaCl+KN0 3 . The reaction is accom- 
plished by boiling together equivalent quantities of strong 
solutions of the two salts. In accordance with the law of 
insolubility the least soluble salt at the boiling temperature 
(NaCl) is formed and precipitated. The crystallized sodium 



165 

chloride is removed from the hot solution and the liquid 
allowed to cool; during the cooling" the salt least soluble in 
cold water crystallizes out (KN0 3 ). The solubility of the 
sodium chloride is about the same at boiling and common 
temperatures, so that there is no additional separation of it 
by cooling, while the solubility of the potassium nitrate is 
decreased more than six times by the reduction of the tem- 
perature. 

Properties of Potassium Nitrate. Potassium nitrate crys- 
tallizes in six-sided rhombic prisms surmounted by six-sided 
pyramids. It has a cooling and slightly bitter saline taste. 
Heated above its fusing point it evolves oxygen and is 
reduced to the nitrite; at a still higher temperature the 
nitrite is decomposed with evolution of nitrogen and oxygen, 
leaving the oxide of the metal. 

The salt is soluble in less than four times its weight of 
water at 18° C, the solubility increasing very rapidly with 
the temperature; at 100° C. water dissolves nearly two and 
one-half times its weight of the salt. 

Potassium nitrate, like the nitrates generally, is a power- 
ful oxidizing agent. Its formula shows it to contain very 
nearly one-half of its weight of oxygen, five-sixths of which 
are available for the oxidation of the combustible body. It 
is chiefly used in the manufacture of gun-powder and pyro- 
techny. 

Potassium Chlorate ; KC10 3 . This salt is a white crystal- 
line solid and like the nitrate is an oxidizing agent. It parts 
with its oxygen more readily than does the nitrate. At a 
high temperature it acts violently upon combustible bodies. 
If a jet of hydrogen or coal gas be placed upon the melted 
salt, ignition ensues and the gas burns brilliantly. The 
chlorate is much used in pyrotechny. 

The common friction primers for firing cannon contain a 
mixture of the chlorate, sulphur and antimony sulphide 



166 

made into a paste with dissolved shellac. A pull on the lan- 
yard withdraws a little rasp inserted in the primer and thus 
explodes the mixture, which ignites the powder in the lower 
part of the tube, and this communicates the name to the 
charge in the gun. The fact that a mixture of it and sulphur 
explodes by friction prevents its use in the manufacture of 
gun-powder. Its use as an oxidizing agent in matches has 
already been referred to. By heat it is eventually decom- 
posed into potassium chloride and oxygen, 2KC10 3 (heated) 
=KCl+KC10 4 +0 2 ; KC104=KCl+0 4 ; for this reason it is the 
most convenient source for obtaining oxygen in the labora- 
tory, as has already been stated. The chlorate may be 
prepared by the action of chlorine upon the hydroxide. 

Potassium Sulphates. The normal sulphate occurs native asso- 
ciated with the sulphate and chloride of magnesium in the mineral 
karnite from which it may be readily separated. It is also produced as 
a bye product in several industrial operations. Karnite is used as a 
fertilizer and potassium sulphate is used in the manufacture of alum. 

The bisulphate KHS0 4 , can be prepared by the action of sulphuric 
acid upon nitre. It finds use in chemical operations for decomposing 
minerals at high temperature, which are not readily attacked by acids ; 
under these conditions its hydrogen gives place to metals. 

OTHER COMPOUNDS OF POTASSIUM. 

Oxides of Potassium. There are several oxides of potassium, the 
best known of which is K 2 4 . This is the final product of the com- 
bustion of potassium in air or in oxygen. K 2 is thought to result 
when K 2 4 is heated to a high temperature or when the hydroxide and 
potassium are heated together. The evidence of the existence of this 
oxide is deemed by some good authorities as unsatisfactory. 

Potassium forms sulphides whose formulae are, K 2 S, K 2 S 2 , K 2 S 4 , 
K 2 S 5 , and K 2 S 7 . The compound KHS also exists. 

SODIUM; Na; 23. 

Sodium does not occur in a free state in nature. The 
most abundant natural compound of it is the chloride or 
common salt. Sodium, like potassium, in combination with 
silica and aluminutn, is a common constituent of certain 
feldspars which go to make up many igneous and metamor- 



167 

phic rocks — it is not however so abundantly present in the 
rocks as potassium. Sodium also occurs abundantly in the 
native sodium nitrate. 

The discovery of potassium naturally led Davy to the dis- 
covery of sodium which he also isolated in 1807 by a process 
entirely similar to that by which he obtained potassium. 

Sodium is now manufactured in a manner similar to that 
described for potassium, namely by reducing" the carbonate 
with charcoal, Na 2 C0 3 +2C— Na 2 +3CO. By distilling* a mix- 
ture of carbon and sodium hydroxide the reduction takes 
place at lower temperature; the sodium distils over and 
sodium carbonate remains in the retort, 3NaOH+C=Na 2 C0 3 
+H 3 +Na. In Castner's method a mixture of iron and carbon 
is made by heating together tar and haematite iron ore, this 
mixture is sometimes called iron carbide, and is used in the 
process instead of charcoal alone as previously explained. 
The action of the iron is mechanical, serving to keep the 
carbon in contact with the fused hydroxide. 

Metallic sodium is now manufactured in this country by 
the Castner electrolytic process. In this process the sodium 
hydroxide is decomposed by electricity. At this writing the 
details of process cannot be obtained. 

Properties and Uses. Sodium is very similar in proper- 
ties to potassium. It is silver white in color and at ordinary 
temperature can be cut like wax but below 0° C. it is hard. 
It is slightly lighter than water its specific gravity being less 
than .97 and will float upon that liquid. It decomposes water 
with liberation of hydrogen, but inflammation does not gen- 
erally occur. If the water be warmed or the metal be placed 
on a slip of bibulous paper so that it will not move around, 
the temperature will rise sufficiently high to ignite the liber- 
ated hydrogen. The burning of the hydrogen volatilizes 
some of the sodium which gives a yellow color to the flame 
produced. Its action on water is not so energetic as that of 
potassium. 



168 

Freshly cut sodium is very lustrous but is immediately 
tarnished by exposure to the air. Sodium is a very important 
reducing agent, its principal application being in the prepa- 
ration of magnesium, aluminum, and silicon from their 
chlorides. It also finds valuable application when amalga- 
mated with mercury, such amalgam being more efficacious 
than mercury alone in extracting gold and silver from their 
ores. 

Sodium Chloride ; Common Salt ; NaCl. Next to air and 

water this substance is the most essential to the life and 
health of the animal world. In addition to this it is one of 
the most important raw materials in the industrial arts. It 
is used in enormous quantities in the alkali industries and is 
the source of all the chlorine. 

Occurrence. Sodium chloride occurs widely and is abund- 
antly distributed. Immense deposits of it occur in various 
parts of the world. The waters of the oceans contain about 
three per cent of it — the waters of many lakes and springs 
are impregnated with it. 

Preparation of Salt. In several countries salt is mined 
directly from the deposits. The most celebrated mine is that 
of Wielitzka, in Gralicia, near Cracow. This mine has been 
worked for several centuries. It is also mined in Germany, 
in England, and at several places in the United States. 
Rock salt is mined in Louisiana, Kansas, and in Grenesee, 
Wyoming, and Livingston counties, New York. Salt thus 
obtained is generally impure and is purified by solution and 
recrystallization . 

The principal portion of the world's supply of salt is 
obtained by the evaporation of natural or artificial *mmtt.l!uMjL4 
Artificial nrises- are produced by admitting water to contact 
with the salt deposits and pumping it out after it has been 
heavily charged with salt. Both natural and artificial brines 
are often concentrated by exposing a large surface of the 



169 

liquid to the air, and this, in Europe, is accomplished by 
allowing the liquid to trickle over walls or towers of brush- 
wood. The concentration in suitable vessels is then con- 
tinued by artificial or sun heat. In some places in this 
country the evaporation is mainly by sun heat alone, being- 
carried on in shallow wooden vats. This is the process at 
Syracuse, N. Y., and in Bay and Saginaw counties, 
Michigan. At other places in these States the process is 
carried on entirely by artificial heat and known as the pan 
process. 

In warm climates, France especially, considerable salt is 
obtained by the evaporation of sea water. This is accom- 
plished in the marshes along the shore into which the water 
is admitted from the sea. As concentration is increased the 
liquid is let from one basin to another until it reaches the 
crystallizing area. 

In cold countries salt is sometimes obtained from sea 
water by exposing the water in shallow pits and allowing it 
to freeze. A large portion of the water may thus be sepa- 
rated and the solution left may be strong enough to pay for 
evaporation by artificial heat. 

In all these processes the purity of the salt depends upon 
the nature of the original brine and other salts are often 
obtained from the brines left (mother liquor), after as much 
common salt has been obtained as practicable. The size of 
the grain of the salt depends upon the temperature at which 
the crystallization takes place, the lowest temperature giving 
the largest grains. 

Properties of Sodium Chloride. The properties of com- 
mon salt are well known. Pure salt is very slightly deli- 
quescent, the presence of magnesium and calcium chlorides 
greatly increases the tendency and they are often present in 
table salt. It is soluble in a little less than three times its 
weight of water at 0° C, and its solubility is very slightly 
increased by raising the temperature. 



170 

Sodium Carbonate; Na 2 C0 3 . Preparation. Before the 
French Eevolution this salt was obtained from the ashes 
of sea weeds. The necessities of the French nation led 
Napoleon to offer a reward for the discovery of some other 
method for preparing" it. This appeal was answered by 
Leblanc in the discovery of a method of making it from 
common salt which not only cheapened the production of 
sodium carbonate but produced the most beneficial results 
upon many other manufacturing industries. It led to im- 
provements in the manufacture of sulphuric acid; it cheap- 
ened the production of hydrochloric acid and chlorine for 
bleaching, thus benefitting the manufacture of all textile 
fabrics; it gave a tremendous impulse to the industries of 
glass and soap making. 

Leblanc Process. A full description of a manufacturing 
plant can not here be attempted. Only the essential re- 
actions involved will be given. The Leblanc process 
consists of three steps. 1st, The conversion of common salt 
into sodium sulphate by heating it with sulphuric acid, 
2NaCl+H 2 S0 4 =Na 2 S0 4 4-2HCl; the sodium sulphate is called 
the salt-cake and the process the salt-cake process. 2nd, 
The conversion of the sodium sulphate into the carbonate by 
heating it with powdered coal and limestone, the reactions 
may be indicated by the reactions — Na 2 S04+C 2 =Na 2 S+2C0 2 ; 
Na 2 S+CaC03 : =CaS+Na 2 C03 — the result of this process is 
called black-ash because of the dark color, from the carbon 
of the mixture of calcium sulphide and sodium carbonate. 
3rd, The last step in the process is the extraction of the 
sodium carbonate from the black-ash by lixiviation with 
water, evaporation to the crystallizing point, and calcination. 

The salt thus obtained usually contains some common 
salt, some sodium sulphate, and some sodium hydroxide, the 
latter resulting from the action of the lime upon the sodium 
carbonate. To obtain pure carbonate the calcined soda is 
subjected to further treatment. 



171 

Solvay 's Process. This process which has now largely 
replaced the Leblanc, depends upon the fact that if a solu- 
tion of the acid carbonate of ammonium be brought into 
contact with a saturated brine solution double decomposition 
ensues, the less soluble acid carbonate of sodium being 
formed and crystallizing out, while ammonium chloride 
remains in solution. The result is accomplished by saturat- 
ing a strong brine solution first with ammonia and then 
carbon dioxide, when the acid sodium carbonate is pre- 
cipitated, NaCl+NH 3 +C0 2 +H 2 0=NaHC0 3 +NH 4 Cl. 

By heat the acid sodium carbonate is converted into the 
normal carbonate, 2NaHC0 3 (heated) =Na 2 C0 3 +C0 2 +H 2 0. 
The C0 2 liberated in this operation is again used in the first 
step of the process. The NH 4 C1 is decomposed by lime and 
the ammonia is used again, 2NH 4 Cl+CaO = CaCl 2 +2NH 3 + 
H 2 0. 

The manufacture of the carbonates by the Solvay process 
at Syracuse, N. Y., and at Saltville, Va., is now conducted 
on a large scale. Other extensive works for this process are 
being erected at Detroit and Cleveland. 

From the reactions indicated in the above processes it 
will be observed that in the Leblanc method the sulphur is 
finally left combined with calcium forming calcium sulphide 
and in the Solvay process the chlorine is left combined with 
the same metal forming calcium chloride both of which pro- 
ducts are of themselves worthless. This waste of raw 
material is a loss in economy of manufacture, and methods 
have been devised by which the sulphur and chlorine are 
recovered for continual use. 

The carbonate is also prepared to a small extent from 
cryolite, which is a double fluoride of sodium and aluminum. 

Properties and Uses of Sodium Carbonate. The normal 

carbonate crystallizes in oblique rhombic prisms containing 
ten molecules of water of crystallization (Na a COs,10 Aq.). In 
dry air the salt effloresces and crumbles to a powder losing the 



172 

greater part of the water of crystallization; when heated all 
the water of crystallization is driven off. The carbonate is 
very sohible in water. 

100 parts of water at 14° C. dissolve more than half their weight of 
the. 10 Aq. salt. The solubility of this salt increases up to 36° C. but 
then decreases. At the boiling point water dissolves nearly four times 
its weight of the salt. 

The salt is less soluble than potassium carbonate and is 
often called washing soda. It is made in enormous quantities 
for use in the manufacture of giass and soap. 

The Acid Carbonate; Bicarbonate; NaHC0 3 . This salt is 
produced as described above in the Solvay process. It may 
also be produced by passing C0 2 into a solution or over crys- 
tals of the normal carbonate. It is used in medicine and 
quite extensively in the preparation of effervescing drinks. 

Both these carbonates are found impregnating the waters 
of certain lakes. Lake Mono is an example in our own 
country. , 

Sodium Hydroxide ; NaOH. This salt may be prepared by 
the action of lime upon a solution of sodium carbonate, the 
reaction being entirely similar to that for the preparation of 
potassium hydroxide, Na 2 C0 3 4-Ca(OH) 2 =2XaOH+CaC0 3 . 

Sodium hydroxide is very similar to that of potassium. It 
is the form to which the carbonate is generally converted 
preparatory to its use in the making of hard soap, it is then 
called soda-lye. Caustic soda is now produced from common 
salt by electrolysis. 

By the action of the electric current upon a solution of 
salt the chlorine is liberated and an amalgam of sodium and 
mercury formed. By mechanical means the amalgam is 
transferred to another compartment of the cell containing 
water, where the sodium is transformed into the hydroxide 
and the mercury returned to the first compartment for 
reamalgamation. In one compartment the mercury is the 
cathode and in the other the amalgam is the anode. 



173 

Sodium Nitrate; NaN0 3 . This salt occurs abundantly 
native associated with other salts, gypsum and common salt. 
It is found in enormous quantities in Chili and Peru and is 
known as cubic nitre or Chili saltpetre. It is purified by 
solution and crystallization. The pure salt is deliquescent 
and very soluble in water. The deliquescent property 
prevents its use in gun-powder but it is largely used in the 
manufacture of potassium nitrate and nitric acid. 

Borax, Sodium Biborate; Na 2 0,2B 2 3 . This substance occurs as 
a native mineral under the name of borax or tincal. It is also obtained 
from other native borates. Tincal and other native borates are 
obtained in large quantities from the salines or marshes of southern 
California and Nevada. These marshes are remnants of former fresh 
water lakes. It also occurs abundantly in the waters of Clear Lake, 
California. In California true veins of calcium borate have been found 
and worked for conversion into borax. Borax may be made by acting 
on sodium carbonate with boracic acid and most of the borax of com- 
merce is so made. 

Borax is an acid salt and when fused dissolves many oxides 
forming glassy beads which often have characteristic colors. This 
action makes it valuable in blow-pipe tests in mineralogy — upon the 
same property depends its use for soldering metals. It is now used in 
considerable quantities in glazing porcelain and earthen ware and in 
making enamels. 

Sodium Silicate. An artificial combination of sodium and silica 
has long been used under the name of soluble glass. It can be made by 
fusing sand and sodium carbonate together or boiling sand with a 
strong solution of caustic soda under pressure. 

This glass is used to coat wood and render it fire-proof, for wall- 
painting, and frescoing and to make artificial stone. Sand mois toned 
with it, pressed into moulds, dried, and highly heated gives an arti- 
ficial sandstone, the sodium silicate fusing and acting as a cement. 
Any required color may be imparted by mixing the necessary metallic 
oxide with the sand. 

Sodium Thiosulphite ; Na 2 S 2 3 . This salt is largely used in photo- 
graphy. It is commonly known as sodium hyposulphite <n- simply 
"hypo." It is formed as stated on page 141) by digesting sulphur with 
a solution of sodium sulphite, Na 2 S0 8 . 

Sodium Sulphates. There are sulphates of sodium corresponding to 

those of potassium. The normal sulphate Na 2 SO 4 ,10 Aq, known as 
Glauber's sail, is an intermediate product in the manufacture of the 



174 

carbonate. It has a bitter taste and is a strong purgative. The 
formula for the acid or bisulphate is NaHS0 4 , Aq. 

Sodium forms several other compounds very similar to corres- 
ponding ones of potassium which will not be mentioned here. 

AMMONIUM; NH 4 . 

The similarity of certain ammonium compounds to analo- 
gous compounds of potassium and sodium has already been 
mentioned. 

The compounds resulting 1 from the action of acid oxides 
upon ammonia do not form these resembling salts until water 
is added. The true salts of ammonia are formed by the 
action of acids upon ammonia or by double decomposition. 
Many such salts are closely analogous to and isomorphous 
with those of potassium and sodium. In these salts the rad- 
ical NH 4 is substituted for hydrogen and seems to play the 
same part as potassium and sodium in their respective com- 
pounds. 

The above and similar facts have suggested the possi- 
bility of the existence of a compound metal which has been 
named ammonium. This radical NH 4 has never been 
isolated. 

An experiment first made by Berzelius adds some weight 
to the supposition for the existence of a metallic radical. 
The amalgams of mercury have a metallic lustre while the 
compounds of mercury with the non-metals are without 
lustre. Berzelius produced what was thought might be an 
ammonium amalgam with the usual metallic lustre ; the result 
tended to strengthen the belief in an ammonium metal. 
This amalgam may be produced by adding a little sodium 
amalgam to a solution of ammonium chloride*; a lustrous, 
porous, metallic-looking mass rises to the surface. This 
mass was once thought to be a true amalgam of mercury and 
ammonium, but it is now thought that the mercury is merely 



*The sodium amalgam is readily prepared by adding a pellet of 
metallic sodium to a little mercury heated in a test tube. 



175 

inflated by the ammonia and hydrogen from the decomposi- 
tion of the ammonium chloride. The mass soon subsides, 
ammonia and hydrogen escaping. The similarity of the 
ammonia salts to those of sodium and potassium is the 
strongest support for the theory of a compound metal and 
this similarity causes the description of the salts at this 
place. 

SALTS OF AMMONIUM. 

The salts of ammonium are derived almost entirely from 
the ammoniacal liquor of the gas works. This liquor con- 
tains an abundance of the carbonate and sulphide of 
ammonia. When the liquor is distilled with lime the more 
stable base expels the ammonia, which is then collected as 
may be desired. 

AMMONIUM CHLORIDE AND SULPHATE. 

These are the most common and important salts. To 
obtain the first the ammoniacal liquor is distilled with lime 
and the expelled ammonia is conducted into a vessel pon- 
taining hydrochloric acid ; to obtain the sulphate the gas is 
conducted into a vessel containing sulphuric acid; in each 
case the gas is absorbed by the acid and the chloride or sul- 
phate formed and these crystallize from the acid. The 
chloride NH 4 C1 is purified by sublimation and thus obtained 
as a tough, fibrous, and semi-translucent mass, difficult to 
powder. It has no odor but has a sharp saline taste ; it is 
very soluble in water, with great reduction of temperature. 
This salt is valuable in medicine and for many other pur- 
poses and is the salt from which ammonia is generally 
obtained. 

The sulphate (NID2SO4 is manufactured in large quan- 
tity from the gas liquor and is generally purified by solution 
and recrystallization. It is largely used for the preparation 
of manures, of ammonia alum, and of other salts. A solu- 
tion of it in ten parts of water is sometimes used to render 



176 

muslins less inflammable; muslins so treated will not burn 
with flame. 

ACID AMMONIUM CARBONATE, SMELLING SALTS. 

This salt is usually obtained by distilling' a mixture of 
ammonium chloride and sulphate with powdered calcium 
carbonate and collecting the distillate. This commercial 
carbonate is a mixture of the acid carbonate NH 4 HC0 3 and 
the carbamate (NH 3 )2C0 2 . It is largely used in medicine 
and as a baking powder. 

Sal volatile is an alcoholic solution of these salts. A 
strong solution of alcohol dissolves out the carbamate 
leaving the acid carbonate. 

The normal carbonate is .obtained from the commercial 
salt by treatment with strong ammonia. 

AMMONIUM NITRATE. 

This salt is prepared by adding ammonium carbonate to 
dilute nitric acid until neutralization has been reached. It 
can be made to crystallize like potassium nitrate ; it is very 
soluble and is deliquescent, is easily decomposed by heat, 
and largely used in making nitrous oxide. It is a constituent 
of some explosives; Bellite contains it. 

AMMONIUM SULPHIDE. 

There are several sulphides of ammonium the most 
important of which is believed to have the formula (NH 4 ) 2 S, 
It is a compound of great practical utility in the laboratory 
often giving very characteristic precipitates with the solu- 
tions of many metallic salts. 

A solution of this substance is formed by saturating a solution of 
ammonia with hydrogen sulphide and adding an equal quantity of 
the ammonia solution, XH 2 0+NH 3 +H 2 S=NH 4 HS+XH 2 ; NH 4 HS+ 
NH 3 =(NH 4 ) 2 S. 

The ammonia salts are all soluble and volatile and can 
be decomposed at high temperature. They are readily 



177 

recognized by giving off ammonia when gently heated with 
lime, soda, or potash. 

BARIUM, Ba. 

Occurrence and Preparation. Barium occurs abundantly 
in nature as a constituent of heavy spar (BaSOJ and 
witherite (BaC0 3 ) ; these minerals frequently occur in the 
gangue of lead mines. The metal finds no useful applica- 
tion; it is named from the great weight of its compounds 
(Barros, heavy). 

It may be prepared by decomposing the fused chloride by 
the electric current. It is a yellow malleable metal and 
decomposes water at common temperature. 

Barium Chloride ; BaCl 2 . The chloride may be formed by 
dissolving the carbonate in hydrochlorfc acid and evaporating 
the solution. The solution of the compound finds frequent 
use in the laboratory. 

Barium Sulphate ; BaS0 4 . Barium sulphate occurs native 
abundantly as heavy spar. It is produced artificially as a 
precipitate whenever a soluble sulphate is brought together 
in solution with a soluble barium salt. 

The sulphate is used' considerably as a substitute for 
white lead under the name of permanent white. The native 
sulphate is not satisfactory for the purpose and the artificial 
is prepared from heavy spar by heating the powdered 
mineral highly in contact with carbon when the following 
reaction takes place, BaSO^+Ci^BaS+^CO. The sulphide 
thus produced is soluble in water and may be used to pre- 
cipitate the sulphate by the addition of dilute sulphuric acid. 
The artificial sulphate may also be prepared from the car- 
bonate by acting upon it with hydrochloric acid and using a 
solution of the barium chloride thus formed to precipitate 
the sulphate, which is practically insoluble in water. 

Barium Carbonate. The carbonate occurs Dative as witherite. li 
may be prepared artificially by precipitation, by adding an alkaline 
carbonate to a solution of the chloride or by passing carbon dioxide 
12 



178 

through a solution of the sulphide prepared as above described. The 
carbonate is principally used in the preparation of the other salts. 

Barium Nitrate; Ba(N0 3 ) 2 . This salt is prepared by 
acting' upon the carbonate or sulphate with dilute nitric 
acid and evaporating to crystallization. It is used as a 
constituent of certain explosives and in pyrotechny. 

Barium Chlorate; Ba(C10 3 )2. This salt is prepared by 
acting upon the artificial carbonate with a solution of chloric 
acid; it is used in pyrotechny. The salts of barium impart 
green color to flames. 

Barium Hydroxide; Ba(OH) 2 . A solution of the hydroxide 
is used as a reagent in the laboratory. It is a delicate test 
for carbon dioxide, for it becomes turbid by a trace of the 
gas. 

The hydroxide may be prepared by dissolving the oxide in 
water the oxide being obtained by heating the nitrate. On a large 
scale the hydroxide may be made by passing steam and carbon dioxide 
over the sulphide heated to redness and decomposing the carbonate 
thus produced by superheated steam ; the results are indicated by the 
following reactions, BaS+C0 2 +H 2 0=BaC0 3 +H 2 S; BaC0 3 +H 2 0=Ba 
(OH) 2 +C0 2 . 

Barium Sulphide ; BaS. It is prepared as above described. 
It has the property of shining in the dark after exposure to 
light, phosphorescent. 

Properties of Barium Salts. Any soluble barium salt will 
give a precipitate insoluble in nitric acid, with the solution 
of any soluble sulphate ; upon this action is based the use of 
the nitrate and chloride in the laboratory. 

Alkaline carbonate or ammonium carbonate gives a white 
precipitate with the solution of a barium salt, insoluble in 
excess but soluble in nitric acid. 

CALCIUM; Ca"; 40. 

Occurrence. Calcium has not been found in a free state 
in nature, but it is an abundant constituent of several 
mineral compounds. Its compounds occur in many waters 



179 

and also abundantly in the animal and vegetable kingdoms. 
In the mineral kingdom its most abundant compounds are 
the carbonates, the silicates, the sulphates, phosphates, and 
fluorides; in organisms the compounds are mainly the 
phosphate, carbonate, and fluoride. 

Preparation and Properties. Calcium was first prepared 
by Davy (1808) by the electrolysis of the chloride. It has a 
brass yellow color, is harder than lead, and is very malleable. 
It decomposes water at the ordinary temperature but not so 
readily as sodium and potassium. Its specific gravity is 
1.58. It is not used in the metallic state. 

Calcium Carbonate; CaC0 3 . This compound in varying 
degrees of purity, exists in great abundance throughout the 
world. It forms rocky beds of limestone (marble, chalk, 
&c.) of immense thickness and extent. It is the chief con- 
stituent of the shells of mollusks, of egg shells, and of coral 
formations. The wide distribution of this mineral and its 
slight solubility in waters containing carbon dioxide explain 
its presence in many waters which have already been de- 
scribed as hard waters. In its different forms it is widely 
used as a building stone for interior decorating, and for the 
preparation of lime. It is also used in the reduction of iron 
from its ores and in many other metallurgic operations. 

Lime ; CaO. No other metallic oxide is used directly so 
abundantly as lime. Lime is manufactured in enormous 
quantities by burning limestone — that is by decomposing the 
limestone by heat; CaC0 3 ( heated) = CaO -fC0 2 . The car- 
bonate commences to decompose at a red heat, but the 
liberated carbon dioxide must be removed to continue the 
decomposition. The carbonate can not be completely decom- 
posed in a covered crucible. Lime is made in very large 
quantities in many parts of the world by heating limestone 
in rudely constructed kilns. The kilns employed are of 
various forms but always so arranged that the escaping 



180 

furnace gases pass over the heated stone, this being neces- 
sary for the removal of the liberated carbon dioxide. In the 
older furnaces the fires are kept up two or three days and 
nights and then the furnace is allowed to cool and the lime 
raked out. In the modern continuous furnace there are two 
styles of furnace; in one alternate layers of limestone and 
fuel are introduced into the furnace at the top, and the 
burned lime is removed from below; in the other the fuel 
and limestone do not come into contact, there being furnaces 
for the former and separate chambers for the latter. The 
stone is introduced above as the lime is raked out below. In 
all cases the limestone is broken into fragments of the 
proper size, otherwise complete decomposition does not take 
place in the interior of the kiln. In the great fire in New 
York City in 1853 marble columns that had been subjected to 
an intense heat were found unchanged beyond three inches 
from the surface. 

If the limestone contains much argillaceous or siliceous 
matter and has been too highly heated, it is found to con- 
tain glassy masses which refuse to slake; the lime is then 
said to be dead burnt or overburnt. If the lime slakes but 
feebly it shows that it contains foreign substances, silica, 
clay, &c, and is then said to be a poor lime. If the lime 
combines readily with water, largely increasing its volume 
(2% times), evolves much heat, and crumbles to a fine 
powder, it is said to be rich or fat lime. Air-slaked lime has 
been slaked by the moisture from the air. The process is 
necessarily slow, during which time the lime absorbs carbon 
dioxide as well as water ; such lime contains frequently one- 
half its weight of the carbonate. 

Calcium Hydroxide; Slaked Lime; Ca(0H) 2 . This sub- 
stance is formed as above stated by treating fat lime with 
water, CaO + H 2 0=Ca(OH) 2 . The hydroxide is slightly 
soluble in cold water and its solubility decreases rapidly 
as the temperature increases. The solution is used in the 



181 

laboratory for absorbing* and detecting" carbon dioxide in 
gases. It is readily converted into lime by the action of 
heat. 

Slaked lime is nsed for numerous and important pur- 
poses. Its greatest use is in the preparation of mortar and 
for this purpose it has been used from time immemorial. It 
is probably one of the first chemical compounds artificially 
prepared by man. 

Ordinary mortar is made by mixing together slaked lime 
and sand. The hardening of mortar is due to the gradual 
conversion of a portion of the hydroxide into the carbonate. 
Not only does the mortar harden but the whole forms a 
compact layer, attaching itself firmly to the stones between 
which it is placed. It is probable that the silica also in time 
combines with some of the lime forming a silicate and bind- 
ing the whole more firmly together. 

A mortar which has been exposed for only a few years 
contains more unaltered hydroxide than one of longer expo- 
sure, for this reason structures of the middle ages display 
more solidity than more recent ones. The sand in mortar 
prevents excessive shrinkage and favors the penetration of 
the carbon dioxide. Unaltered hydroxide has been found in 
mortars of the Roman era. 

Freshly plastered houses are often uncomfortably damp 
because of the moisture which comes from the walls. The 
moisture is due both to the water mechanically mixed with 
the mortar and to that set free chemically by the conversion 
of the lime into the carbonate, Ca(OH) 2 +C02=CaC0 3 +H 3 0. 
The hardening of the mortar and the drying of the walls can 
be hastened by burning coke in open grates in the closed 
rooms. 

Note. — At 00° F. it requires 800 parts of water to dissolve one pan 
of the hydroxide of calcium, and at '2M° F. it requires 1500 pan 
water to dissolve one of the hydroxide; lime water always giv< 
precipitate when boiled. 



182 

Anhydrous Calcium Sulphate; CaSO*. This substance 
exists in considerable abundance in nature, occurring as a 
native mineral called anhydrite. It is of little importance 
and can not be applied to the uses which make the hydrous 
sulphate so valuable. The hydrous sulphate will now be 
described. 

Hydrous Calcium Sulphate; Gypsum; CaS0 4 ,2H 2 0. This 
compound is met with in considerable abundance in nature 
and the many different varieties are included under the name 
of gypsum. Grypsum occurs in considerable abundance in 
natural beds. It is slightly soluble in water, being most sol- 
uble when the water is at the temperature of 35° C. (1 part 
in 400). It is this substance in solution which produces the 
permanent hardness of water, already referred to. 

When gypsum is heated to near 200° C. it loses three- 
fourths of its water, 2 CaS0 4 ,2H 2 0= (CaS0 4 ) 2 ,H 2 0+3H 2 ; and 
then constitutes plaster of Paris so named because obtained 
in large quantities from quarries near that city. When the 
plaster of Paris is ground to powder and mixed with water 
to a paste it combines with the water to reproduce gypsum 
evolving heat, expanding, and rapidly setting to a hard 
mass. If the gypsum is heated to above 200 C, all its water 
is driven off and it loses the property of taking it up rapidly 
again. Such overburnt gypsum is valueless for the use of 
the ordinary plaster. 

The properties of the plaster give it many useful applica- 
tions. It is extensively used in making moulds and casts, 
statuettes, copies of coins, medals, &c, for the interior 
finish of walls and ceilings, and for the plaster bandages of 
surgeons. Ten per cent of lime added to the- plaster accele- 
rates the setting and increases the hardness. If the plaster 
be moistened with a strong solution of alum instead of water 
the setting is delayed and allows more time for manipulation. 

Stucco consists of plaster of Paris mixed with a solution 
of glue or gelatine; it solidifies more slowly and becomes 



183 

hard enough to polish. Stucco may be given different colors 
by mixing- with various metallic oxides. 

When plaster of Paris is exposed to moisture it regains 
part of its water and accordingly deteriorates in value. 

Plaster of Paris (burnt gypsum) is also a valuable fertili- 
zer, its action is thought to be due to its power of absorbing 
ammonia and volatile compounds of ammonia thus rendering 
them more available for plant food. 

Calcium Chloride ; CaCl 2 . This compound is obtained as 
a bye-product in certain chemical operations. It may be 
readily obtained by acting upon pure calcium carbonate with 
hydrochloric acid and evaporating the residue to crystal- 
lization. The powdered crystals mixed with snow or ice are 
used for artificial production of cold. When the chloride has 
been highly heated (200° C.) it is very efficient in drying 
gases and thus finds frequent use in the laboratory. 

Calcium Fluoride ; CaF 2 . This substance occurs as- a nat- 
ural mineral and is the most important source of hydrofluoric 
acid, already described. 

Calcium Sulphide ; CaS. This compound has the property 
of phosphorescing after exposure to light like barium sul- 
phide. It is one of the constituents of certain luminous 
paints. The phosphorescence is not due to oxidation, since 
it is shown in a specimen that has been hermetically sealed 
for more than a century. It is now believed that the phos- 
phorescence is due to impurities and that chemically pure 
sulphide does not show it. 

Other Compounds of Calcium. There are many other 

compounds and salts of calcium the most common of which 
are the phosphates and the silicates. Certain of these are 
natural minerals and are of great importance in economic 
mineralogy and geology. 

Reaction of Calcium Sails. Solutions of calcium salts 
give a white precipitate with alkaline carbonates, insoluble 



184 

in excess of the carbonate bnt soluble in nitric acid. They 
give white precipitates with soluble oxalates, soluble in 
acetic acid. 

MAGNESIUM; Mg. 

Occurrence of the Element. Magnesium does not occur 
native but occurs widely distributed in the combined form in 
many minerals. The most important of these are the car- 
bonates and silicates of magnesium, more or less pure. 
Serpentine and talc are examples of the latter and dolomite 
of the former. Dolomite or mag^nesium carbonate is a 
double carbonate of calcium and magnesium. It occurs in 
immense beds and in places forms entire mountain masses. 

Preparation, Properties and Uses. The metal may be 
prepared either by electrolysis of the fused chloride or by 
the decomposition of the chloride with sodium. It is a silver 
white metal, is malleable, but is ductile at only high temper- 
ature. It is pressed into wire in a semi-fluid state and after- 
ward flattened into ribbon, in which form it is generally 
used. Its specific gravity is 1.75. It melts at a little below 
a red heat and is easily volatilized. In dry air it retains its 
lustre, but in moist air it soon becomes covered with a gray 
coating of oxide, which prevents further action. 

In the form of ribbon or wire it takes fire in the air a 
little above a red heat and burns with great brilliancy, pro- 
ducing the oxide (MgO). To insure the combustion the 
unburned portion must be kept in the flame of the burning 
part or in contact with other flame. There are lamps 
specially constructed to accomplish these results. 

The magnesium flame gives a continuous spectrum, which 
is rich in chemical rays (rays of great refrangibility) . 
Because of this property the light may be used for photo- 
graphic purposes in the absence of sunlight. For photo- 
graphic purposes it has recently been largely superseded by 
electric light. It is still used extensively for signal lights 
and in flash-light cartridges for instantaneous photography. 



185 

Magnesia; MgO. This is the only oxide of magnesium. 
It is always produced when magnesium is burned in air. It 
is a white light powder, infusible except at the highest 
temperatures, and almost insoluble in water. It is a strong 
base and neutralizes acids in the most complete manner, 
though alkalinity is not shown by the taste. The oxide finds 
frequent use in medicine. On account of its infusibility it is 
largely used in the manufacture of crucibles, cupels, and 
fire-bricks. 

Magnesium Sulphate; MgS0 4 ; Epsom Salts. The mag- 
nesium sulphate, the form known as Epsom salts occurs in 
many mineral waters. It derives its name from the Epsom 
springs in England. It is abundant in Hunyadi water. This 
salt was formerly prepared by acting upon dolomite (double 
carbonate of calcium and magnesium) with sulphuric acid. 
The calcium sulphate produced being very insoluble is easily 
separated from the magnesium sulphate. By far the greater 
portion of the commercial sulphate is now prepared from the 
native sulphate of the Stassfurth salt beds. By exposing 
this native and nearly insoluble salt to the action of water it 
is converted into the soluble Epsom salts. The sulphate is 
used in medicine as a purgative, and largely as warp sizing 
in the cotton trade. 

The composition of Epsom salts is expressed by the formula Mg 
S0 4 ,7H 2 G. Of this water six molecules are removed at 150° C, while 
the remaining one is driven off at 200° C. The native salt of the Stass- 
furth beds called Kieserite has the composition MgS0 4 ,H.,0. 

Other Compounds of Magnesium. There are many other compounds 
of magnesium among which may be mentioned the chloride (MgCl 2 ) 
and the hydroxide Mg(OH) 2 . The former occurs in many natural 
waters and is an important source of the metal. The hydroxide is 
much used in Europe for extracting stigar from molasses. 

The carbonate occurs as a natural mineral, inagnesite <and tin 1 sili- 
cate occurs in talc, serpentine, mica, and several other minerals. The 
phosphate of magnesium is present in small quantities in bones and in 
certain seeds. The borate also occurs in nature. 



186 

ZINC; Zn"; 65. 

Occurrence. Native zinc has been reported from a few 
places (South Africa, Australia, and Alabama) but the 
reports lack verification. If found at all in the free state it 
is in very small quantity. It occurs quite abundantly as a 
constituent of certain natural compounds, the most im- 
portant of which are the common ores of zinc — zinc oxide, 
ZnO; zinc carbonate, ZnC0 3 ; zinc sulphide, ZnS. 

The miner alogical names for these ores are for the oxide, zincite,for 
the carbonate, smithsonite or calamine, and for the sulphide zinc blende 
or sphalerite. 

Metallurgy of Zinc. The extraction of zinc from its ores 
is simple in principle but owing to certain properties of the 
metal its reduction requires distinctive arrangements. Zinc 
is fusible and volatile at such moderate temperature and so 
readily combustible in air that its ores can not be reduced 
like those of the other common metals, in an open furnace — 
in such furnace the zinc would be volatilized and burnt. 

If the ores to be used for the extraction of the metal are 
the carbonate and sulphide, they are first converted into the 
oxide. To accomplish this the carbonate is calcined to expel 
moisture and carbon dioxide. The sulphide is roasted for 
several horns with continual stirring during which the 
sulphur is oxidized to sulphur dioxide and passes off. In 
each case the ore is left in the form of zinc oxide. 

The extraction of the metal from the zinc oxide is ac- 
complished by heating it with charcoal in specially con- 
structed vessels of fire-clay. These retorts are connected 
with suitable receivers of the same or different material in 
which the zinc is collected. The carbon removes the oxygen 
from the ore forming carbon monoxide which escapes. The 
zinc volatilizes and is condensed in the receiver, the reaction 
being ZnO-f C=Zn-f CO. 

At the beginning of the operation before the receivers 
have become hot the zinc deposits as a fine powder known as 



187 

zinc dust. This dust is a powerful reducing" agent and is 
used in the arts as well as in the laboratory. As the process 
progresses the zinc collects in drops and then in the liquid 
state and is removed at stated intervals. The zinc obtained 
from the furnace condensers is usually impure, containing 
small quantities of the other metals lead being" the most fre- 
quent impurity. For purification the spelter is remelted and 
the lead separated by virtue of its great specific gravity. 

In some of the modern furnaces the carbonate is intro- 
duced into the retorts without previous calcining; the carbon 
dioxide is driven off long before the temperature of reduction 
is reached in the retort. 

There are other methods employed for extracting zinc from the 
poorer varieties of ore. They maybe included under the term "wet" 
processes and are not suitable for description here. 

Properties of Zinc. Zinc is a bluish-grey metal of well 
known appearance ; it is a little lighter than iron the specific 
gravity being about 7. Under ordinary circumstances zinc 
is brittle, but between 120° and 150° C. it is malleable and 
may be rolled and hammered and after such treatment it 
retains its malleability when cold. At 200° C. zinc again 
becomes brittle. 

Until the beginning of the century zinc was only used to 
form alloys because prior to that time the manner of making 
it malleable was not known. At a bright red heat zinc boils 
and volatilizes and if air be admitted burns with a bluish- 
green light producing zinc oxide. 

Zinc is soon tarnished in moist air becoming coated with 
the oxide which is gradually converted into a basic carbon- 
ate. The coating tends to protect the zinc from other action 
and renders it more durable. Commercial zinc is readily 
acted upon by dilute acids and at the boiling temperature 
decomposes water. 

Pure zinc is not attacked by boiling water and is scarcely affected 
by either dilute or concentrated hydrochloric or sulphuric acid. Nitric 



188 

acid and the alkalies attack pure zinc. Impure zinc amalgamated with 
mercury resists the action of the acids just as does the pure zinc. 

Uses of Zinc. Zinc is one of the highly nsefnl metals. 
On account of its greater durability it is largely used to 
coat iron. Iron coated with either zinc or tin is commonly 
said to be galvanized. Zinc while it lasts acts more perfectly 
than tin ; when tin is used the protection is effective only so 
long as the surface of the tin is unbroken. As soon as the 
iron is exposed the oxidation proceeds more rapidly than if 
the tin were not there. A coating of zinc protects so long as 
the zinc lasts. The difference in the action of these two 
metals is due to their different electrical relations to iron. 
By the above use of zinc its durability is combined with the 
great strength of iron. 

The coating of iron plates with zinc is accomplished by 
producing a chemically clean surface on the iron and then 
dipping it into melted zinc. The surface of the melted zinc 
is covered with sal-ammoniac which prevents the bad effects 
which would result from the zinc oxide there formed.* 

Zinc melts at a low temperature and its casting's take a 
sharp impression of the mould. For these reasons it is used 
for many structural purposes where ornament rather than 
strength is considered. It has thus found general applica- 
tion in some countries for the preparation of statuettes, 
monuments, and other objects of beauty which .can be 
bronzed or given any desired color. The recent process 
of photo-engraving consumes a considerable quantity of 
specially prepared sheet zinc. Zinc is used to a considerable 
extent for roofing and gutters and in electric batteries. Zinc 
dust is used industrially and in the laboratory as a reducing 
agent. 

Zinc forms useful alloys with many metals, the most 

*The sal-ammoniac (NH 4 C1) dissolves some of the zinc forming zinc 
chloride with liberation of ammonia. The zinc chloride dissolves the 
zinc oxide and prevents any of it adhering to the iron. 



189 

important of which are brass (copper and zinc) and german 
silver (nickel, zinc and copper). 

Zinc Oxide; ZnO. Zinc forms but one oxide, ZnO. The 
oxide occurs as a red mineral zincite. The native oxide is 
only used as an ore of zinc. The artificial oxide is formed 
by the combustion of zinc in air. The zinc fumes are led 
into condensing chambers and the oxide is deposited as a 
powder. It is a white tasteless powder usually called zinc- 
white. It is used as a paint and while it has not the cover- 
ing power or body of white lead, it does not change color by 
the action of sulphuretted hydrogen, the sulphide of zinc 
being white. Zinc white is also used in pharmacy and in the 
manufacture of certain kinds of glass. 

The oxide is a strong base readily acted upon by acids forming- salts 
isomorphous with those of magnesium. When the oxide is heated it 
turns yellow but is white again upon cooling. It is insoluble in water 
and very difficult to fuse. The oxide may be formed by decomposing 
the artificial carbonate by heat, the latter being precipitated from a 
solution of the sulphate by means of an alkaline carbonate. 

Zinc Sulphate; ZnS0 4 ; White Titriol. The sulphate is 

prepared on a large scale by the oxidation of the native 

sulphide. The sulphide is roasted in air and the sulphate 

formed is dissolved out with water and crystallized. The 

sulphate has a disagreeable taste and is used medicinally as 

an emetic ; it is also used in dyeing, in calico printing, and 

in the manufacture of varnishes. 

The formula of the sulphate is ZnS0 4 ,7H 2 0. At 100° C. it loses all 
the water except one molecule. It requires a much higher temperature 
to expel this last molecule. 

Zinc Chloride ; ZnCl 2 . The chloride is prepared by acting 
upon zinc or zinc oxide with hydrochloric acid and evapo- 
rating to crystallization. It is very deliquescent and its 
solution will dissolve paper and cotton. If zinc oxide be 
dissolved in a strong solution of the chloride, the solution 
will dissolve wool and silk. 



190 

Burnett's disinfecting fluid is a solution of zinc chloride. 
It absorbs sulphuretted hydrogen and ammonia and other 
offensive gases resulting from putrefaction. It is effective in 
arresting the decomposition of animal and vegetable sub- 
stances. The chloride is used as a caustic in pharmacy and 
to a certain extent in the weighting of cotton goods. 

Other Compounds of Zinc. Of the other compounds of zinc, the 
most important are the carbonate and sulphide. Their occurrence and 

use as ores have already been mentioned. A hydrate of zinc ZmOHu 
is precipitated whenever alkaline hydrates are added to solutions of 
zinc salts. A silicate and a phosphate of zinc occur as natural minerals. 

Reactions of Zinc Salts. Caustic potash and soda and 
ammonia give a white precipitate insoluble in excess. 
Ammonium carbonate gives a white precipitate soluble in 
excess. 

Hydrogen sulphide gives no precipitate with solutions of 
zinc salts when free mineral acids are present. TTitli neutral 
solutions or with salts of the organic acids and zinc the sul- 
phide of hydrogen gives a white precipitate. 

Ammonium sulphide gives a white precipitate with solu- 
tions of zinc salts insoluble in caustic alkalies. This white 
sulphide distinguishes zinc from all other common metals. 

ALUMINUM. 

Occurrence. Aluminum has not been found in the free 
state, but it is a widely distributed constituent of many nat- 
ural mineral compounds. These compounds are simple or 
complex silicates, and the most abundant and important are 

clay, felspar, and the micas. The felspars are constituents 
of many of the most common and important rocks, granite, 
gneiss, and others. By the natural decomposition of fels- 
pathic rocks clays of varying degrees of purity result, the 
purest form being knowu as kaolin. Pure kaolin is a 
hydrated silicate of aluminum. Common clay is kaolin 
mixed with sand and colored by iron oxide and other impur- 
ities. Another important and frequently occurring natural 



191 

compound containing aluminnm as a constituent is cryolite, 
a double fluoride of sodium and aluminum. Aluminum sul- 
phate in the form of alum is found in certain waters. Alumi- 
num is one of the most abundant constituents of the earth's 
crust. 

Preparation of Aluminum, Aluminum is now prepared 
mainly by electrolysis, especially is this the method in this 
country. A powerful electric current is sent through a bath 
of cryolite (a double fluoride of sodium and aluminum) in 
which aluminum oxide (A1 2 3 ) is dissolved. The metal is 
deposited at the cathode, the cryolite being kept fused by 
the heat of the current. The alumina used is artificially 
prepared. 

Until recently and still to a certain extent in Europe, aluminum was 
prepared by reducing the double chloride of aluminum and sodium with 
metallic sodium. 

An electrical process for making aluminum alloy is used 
extensively in this country ( Co wles' process). In this pro- 
cess the aluminum oxide is mixed with carbon and the mass 
subjected in a furnace to the passage of a strong current of 
electricity. Under the intense heat the oxide is reduced but 
to collect the metal in a single fluid mass, it is found neces- 
sary to add copper or iron to the charge of the furnace and 
the alloys of these metals are then obtained. 

Properties and Uses of Aluminum. Aluminum is a 
remarkable metal in that its specific gravity is 2.56 and yet it 
possesses many of the properties of the most useful metals. 
It is a white metal not acted upon by dry or moist air at the 
common temperature. It is very sonorous and has great 
tensile strength. It is ductile and malleable and can be 
beaten into leaf like gold and silver, but it requires frequent 
annealing during the operation. It is a good conductor of 
heat and electricity. It fuses at 625° C. and contracts upon 
solidifying. 



192 

At high temperature it oxidizes in the air arid in the form of foil will 
burn in the air. Water and steam at high temperature act upon it. 
Nitric acid scarcely acts upon it at all nor does dilute sulphuric acid. 
Strong sulphuric and hydrochloric acids act readily upon it. Organic 
acids do not affect it nor is it acted upon by mercury. 

As the price of aluminum falls its use is constantly ex- 
tending. In some countries many of the soldiers' equipments 
are made of this metal (cooking utensils, canteens, spoons, 
other parts of the mess outfit, buckles, &c.) and it is being 
experimented with for similar use in our service. A con- 
siderable quantity has been employed in Germany for 
cartridge cases to contain smokeless powder, aluminum 
being much less rapidly corroded than copper. It is found 
admirably adapted for certain surgical apparatus (tubes, 
suture-wire, supports, &c). It can also be used to replace 
the more costly platinum in electric batteries. 

In addition to these uses of the pure metal it is used as an 
alloy. The alloy with 80 parts of copper (aluminum bronze) 
approaches steel in strength. Other alloys of it are very 
strong and yet very light. For engineer £ and surveying 
instruments the strong light alloys are admirably adapted. 

Aluminum Sulphate; Al 2 (SOJ 3 , Aq. This salt may be 
prepared by acting upon aluminum hydrate with sulphuric 
acid and evaporating. The sulphate is prepared upon the 
commercial scale by acting upon clay with sulphuric acid. 
Clays (the hydrated silicates of aluminum) differ in their 
availability for the preparation of the sulphate. Bauxite is 
a variety of clay largely used for the purpose in England 
and in France. It is more easily acted upon by the acid but 
contains more iron than China clay or kaolin. 

The sulphate is largely used for the same purposes as the 
alums which are next to be described. Indeed it is the 
presence of this compound in the alums that gives them 
their industrial uses. The common alum (double sulphate 
of aluminum and potassium) is preferable to the single 
sulphate for such uses because its crystalline form makes it 



193 

more difficult to adulterate and besides it is cheaper to 
prepare. 

Alum: Double Sulphate of Aluminum and Potassium; 

A1K(S0 4 )2. Common alum is one of the most important 
artificial compounds of aluminum. This compound may be 
prepared by mixing 1 solutions of the sulphates of potassium 
and aluminum and evaporating* to crystallization. 

Alum is generally prepared in one of two ways : 1st. By 
acting upon clay with concentrated sulphuric acid, by which 
aluminum sulphate is formed. Solution of this sulphate and 
that of potassium sulphate are then mixed in proper propor- 
tions and evaporated. 2nd. From alum shale, which is a 
shale impregnated with small crystals of iron pyrites. It 
also often contains bituminous matter sufficient to make it 
combustible. If the shale itself is not combustible it is 
mixed with some coal and made into long heaps. The piles 
of shale are then lighted and undergo a smothered combus- 
tion, which results in the formation of the^ sulphates of potas - c*l* 
«ium and iron. These sulphates are dissolved out and mixed 
with solution of potassium chloride when double decomposi- 
tion takes place between the iron and potassium salts with 
the formation of potassium sulphate and iron chloride. By 
evaporation the alum crystallizes from the solution. Potas- 
sium sulphate may be used instead of the chloride, but 
if there be much ferric sulphate an iron alum is formed 
which is isomorphous with and contaminates the potas- 
sium alum. The action in the shale heap consists in the 
oxidation of the iron pyrites with the formation of iron sul- 
phate and sulphuric acid. The sulphuric acid attacks the 
clay forming A1H(S0 4 )2. In some cases with certain shales 
this action takes place by mere exposure to the air without 
any combustion. 

A considerable amount of alum is also made from the 
natural mineral alunite. This substance may be considered 
as a basic ahmi with more alumina than the common alum. 



194 

By calcining" and treating with water common alum is dis- 
solved out, or by acting upon the alunite with sulphuric acid 
and adding the proper amount of potassium sulphate. 

The alunite may be considered as a compound of one molecule of 
anhydrous alum and one of aluminum hydrate ; it may then be repre- 
sented by the formula, ALK(SO, 4 ) 2 ,Al(OH) 3 . 

Ammonia Alum. Ammonium sulphate may be used 
instead of potassium sulphate in the preparation of alum 
with the production of ammonia alum instead of potash 
alum. The two salts are entirely similar except that the first- 
contains the radical NH 4 instead of K. This alum is manu- 
factured at certain places where the ammonium sulphate is 
cheaper than the potassium sulphate. The ammonium alum 
answers equally -as well as the potash alum in its most 
important applications. At one time in England large quan- 
tities of this alum were made. 

Alum is very largely used in the preparation of pigments, 
as a mordant in dyeing and calico printing, in paper making, 
in clarifying water, and in the preparation of leather. Burnt 
alum which is used medicinally is prepared by heating com- 
mon alum to a dull red heat driving off the water of crys- 
tallization. 

Alumina; Aluminum Oxide; A1 2 3 . Alumina is found in 
nature as corundum, a mineral next to diamond in hardness. 
Emery is an impure form of alumina. The ruby and sap- 
phire are composed of nearly pure alumina. 

Alumina may be prepared artificially by strongly heating -co &ira& n 
alum ; it is left as a white insoluble powder. Alumina is a very weak 
base so that its salts may exhibit acid properties. 

Aluminum Hydroxide; Al 2 (0H) 6 . If solutions of alum- 
inum salts (alum may be used) be treated with ammonia or 
alkaline carbonate, a white gelatinous precipitate is formed 
which may be dried to a soft friable mass. This hydroxide 
has a very powerful attraction for organic matter and when 
digested with solutions of vegetable coloring matters it com- 



195 

bines with and carries down the coloring matters leaving" the 
liquid clear if the hydroxide be in sufficient quantity. The 
compounds resulting 1 from the combination of the hydroxide 
and the coloring matters are called lakes. The fibres of 
cotton may be impregnated with the hydroxide and may then 
be permanently dyed. The aluminum compound has affinity 
both for the fibre and the coloring matter. Bodies thus used 
to fix the coloring matters are called mordants, hence the use 
of aluminum salts as mordants. Other compounds of alum- 
inum besides the hydroxide have this property and will be 
again noticed. 

Other Compounds of Alumina. The silicates of aluminum form a 
large and important class of minerals as already stated. Among the 
less important compounds of this element are the chloride, fluoride, and 
sulphide. 

Thallium. This element was discovered in 1861 by means of the 
spectroscope. Its discovery was among the first applications of the 
spectroscopic method. Thallium resembles lead in its physical prop- 
erties, in the character of its sulphide, and of its haloid salts. It 
resembles the alkali metals in its soluble hydrate and carbonate. But 
its chloride is nearly insoluble in which it is related to silver, but 
because of the relation between its properties and its atomic weight it 
is classed with the aluminum group. None of its compounds have 
found useful application. Its salts are poisonous and impart a green 
color to flame. 

IRON; Fe; 56. 

Occurrence. Iron is the most useful of the metals. It is 
only rarely found in the metallic or pure state. Metallic iron 
is usually the chief constituent of meteorites, those metallic 
masses which occasionally fall upon the surface of the earth. 
Meteorites generally contain several other elements among 
which are nickel, cobalt, and chromium. Meteorites weigh- 
ing as much as 20 tons have been found. Native iron lias 
also been found disseminated in grains and in large masses 
through certain igneous rocks. 

As a constituent of natural compounds iron is very widely 
diffused. It can be detected in nearly all rocks, in manv 



194 

By calcining and treating' with water common alnm is dis- 
solved out, or by acting upon the alunite with sulphuric acid 
and adding the proper amount of potassium sulphate. 

The alunite may be considered as a compound of one molecule of 
anhydrous alum and one of aluminum hydrate; it may then be repre- 
sented by the formula, ALK(S0 4 ) 2 ,Al(OH) 3 . 

Ammonia Alum. Ammonium sulphate may be used 
instead of potassium sulphate in the preparation of alum 
with the production of ammonia alum instead of potash 
alum. The two salts are entirely similar except that the first 
contains the radical NH 4 instead of K. This alum is manu- 
factured at certain places where the ammonium sulphate is 
cheaper than the potassium sulphate. The ammonium alum 
answers equally -as well as the potash alum in its most 
important applications. At one time in England large quan- 
tities of this alum were made. 

Alum is very largely used in the preparation of pigments, 
as a mordant in dyeing and calico printing, in paper making, 
in clarifying water, and in the preparation of leather. Burnt 
alum which is used medicinally is prepared by heating com- 
mon alum to a dull red heat driving off the water of crys- 
tallization. 

Alumina; Aluminum Oxide; A1 2 3 . Alumina is found in 
nature as corundum, a mineral next to diamond in hardness. 
Emery is an impure form of alumina. The ruby and sap- 
phire are composed of nearly pure alumina. 

Alumina may be prepared artificially by strongly heating <cnmni nu 
alum ; it is left as a white insoluble powder. Alumina is a Tery weak 
base so that its salts may exhibit acid properties. 

Aluminum Hydroxide; Al 2 (0H) 6 . If solutions of alum- 
inum salts (alum may be used) be treated with ammonia or 
alkaline carbonate, a white gelatinous precipitate is formed 
which may be dried to a soft friable mass. This hydroxide 
has a very powerful attraction for organic matter and when 
digested with solutions of vegetable coloring matters it com- 



195 

bines with and carries down the coloring* matters leaving" the 
liquid clear if the hydroxide be in sufficient quantity. The 
compounds resulting- from the combination of the hydroxide 
and the coloring* matters are called lakes. The fibres of 
cotton may be impregnated with the hydroxide and may then 
be permanently dyed. The aluminum compound has affinity 
both for the fibre and the coloring matter. Bodies thus used 
to fix the coloring matters are called mordants, hence the use 
of aluminum salts as mordants. Other compounds of alum- 
inum besides the hydroxide have this property and will be 
again noticed. 

Other Compounds of Alumina. The silicates of aluminum form a 
large and important class of minerals as already stated. Among the 
less important compounds of this element are the chloride, fluoride, and 
sulphide. 

Thallium. This element was discovered in 18(51 by means of the 
spectroscope. Its discovery was among the first applications of the 
spectroscopic method. Thallium resembles lead in its physical prop- 
erties, in the character of its sulphide, and of its haloid salts. It 
resembles the alkali metals in its soluble hydrate and carbonate. But 
its chloride is nearly insoluble in which it is related to silver, but 
because of the relation between its properties and its atomic weight it 
is classed with the aluminum group. None of its compounds have 
found useful application. Its salts are poisonous and impart a green 
color to flame. 

IRON; Fe; 56. 

Occurrence. Iron is the most useful of the metals. It is 
only rarely found in the metallic or pure state. Metallic iron 
is usually the chief constituent of meteorites, those metallic 
masses which occasionally fall upon the surface of the earth. 
Meteorites generally contain several other elements among 
which are nickel, cobalt, and chromium. Meteorites weigh- 
ing as much as 20 tons have been found. Native iron has 
also been found disseminated in grains and in large masses 
through certain igneous rocks. 

As a constituent of natural compounds iron is very widely 
diffused. It can be detected in nearly all rocks, in nianv 



196 

minerals, and is present in the coloring matter of common 
clay and soils generally. The oxides, carbonate, and sul- 
phide of iron are found abundantly and constitute the ores 
of iron. 

OKES OF IKON. 

Ores of a metal are the natural compounds of this metal 
which are worked to obtain the metal. The ores of iron are 
the following: 

Chemical Name. Common or Mineral Name. Composition. 

/Ferric oxide or /Hsemetite or \-p q 

\Iron sesqui-oxide, \ Specular iron ore, j 2 3 * 

Ferroso-ferric oxide, Magnetic oxide or magnetite, Fe 3 4 . 

Ferric hydrate, Limonite or brown hsemetite, 2Fe 2 3 ,3H 2 0. 

Ferrous carbonate. Spathic ore,^ *™^° d ne }FeCO,. 
*Iron bisulphide, Iron pyrites, FeS,. 

*The last is an ore of sulphur mainly hut is sometimes worked for iron. 

These ores frequently contain impurities. The spathic 
when mixed with clay is known as clay iron-stone, when 
with bituminous matter it is called black band. Other im- 
purities are often present which must be wholly or partially 
removed in the. manufacture. Compounds of sulphur and 
phosphorus are very often present and are very objection- 
able in the ores. Pyrites is seldom used as an iron ore but 
is more generally worked for the sulphur. 

METALLURGY OF IKON. 

This important branch of industry usually consists of two 
distinct operations. 1st, The production from the ores of a 
fusible carbide of iron (cast iron).. 2nd, The conversion of 
the cast iron into pure iron (bar or wrought iron). Iron is 
however made direct from the ore. 

Cast or Pig-iron. Cast iron is made by subjecting the 
ores of iron to the action of reducing agents in a blast 
furnace but certain classes of ores often undergo a pre- 
liminary treament before being introduced into the blast 
furnace. 



3-F«,+4C0f 



5F t -rZCJ0*Kfi+<A; 



COfC-LCO 
C+O^CO Z 







197 

Preliminary Treatment of Ores. This treatment consists 
in sorting the ore, breaking it into fragments of the required 
size, and subjecting the ore to a calcination or roasting 
process. The effects of the calcination are 1st, To drive off 
water when present in too large quantity. 2nd, To drive off 
sulphur, arsenic, and other volatile impurities. 3rd, To drive 
off carbon dioxide from spathic ores and to remove carbon- 
aceous matter when there is an excessive amount in the 
black band. 4th, The conversion of the ferrous into the 
ferric oxides. 5th, The ore is left more porous and in better 
condition for the action of the reducing agents in the 
furnace. 

This preliminary treatment is seldom applied to the 
haematite and magnetic ores unless they contain impurities. 
The calcination of the ore is often accomplished in open 
heaps or in rectangular chambers but in the most modern 
method the calcining is conducted in large circular kilns, the 
ore and fuel being charged in at the top — the process being 
continuous. 

The Furnace. The furnaces in which the ore is reduced, 
differ somewhat in form and size depending upon the nature 
of the ore and fuel employed. The capacity of furnaces 
varies from 20,000 to 50,000 cubic feet, the best modern 
furnaces having between 15,000 and 30,000. The height 
varies from 40 to 100 feet, the most recent furnaces being not 
over 85 feet. Fig. shows a section of a modern American 
furnace, being that of one of the furnaces of the Edgar 
Thompson works. This figure also illustrates the manner in 
which furnaces are now supported, upon an iron frame rest- 
ing upon piers. The furnace is jacketed throughout with 
plates of iron or steel riveted together; the furnace is lined 
with fire-brick, these being surrounded by common brick or 
stone. In nearly all modern blast furnaces the top of the 
furnace is closed by some such arrangement (cup and cone) 
as is shown in the figure. This serves to prevent the escape 



198 

of the gas from the top of the furnace and for the better dis- 
tribution of the ore, fuel, fee, charged in at the top. 

The heated gases are drawn off at the top by large pipes 
which lead from the furnace near the top atoove the stock- 
line — these pipes are known as " down comers." The gases 
are used as a source of heat for heating the air fed to the 
furnace and for other purposes. Heated air is forced into 
the furnace through delivering tubes called tuyere pipes, one 
of which is shown at T in the figure. The temperature of 
the tuyere pipe is kept down by causing water to circulate 
through a truncated cone which surrounds it. Arrangements 
are always connected with the furnace for delivering the 
large quantities of raw materials which are introduced at the 
top. For introducing the materials the top of the furnace is 
entirely or partially surrounded by a charging gallery and 
the materials are carried up by some form of hoist or lift, 
unless the furnace is so situated that the gallery can be 
reached by bridge or trestle from higher ground. The slope 
of the furnace is that which experience has shown to be the 
best for the production and proper distribution of the 
required temperature conditions and for the proper move- 
ment of the materials charged into the furnace at the top 
and bottom. 

The Fuel. The fuels used in blast furnaces are coke, 
anthracite coal, charcoal, and in certain localities some varie- 
ties of bituminous coal. 

Reduction of the Ore. When the furnace is first started 
it is said to be " blown in." For this purpose the furnace is 
charged with coke or coal, with wood at the bottom. A 
gentle blast is first employed so as to gradually raise the 
temperature and to produce regular expansion in drying and 
when the fuel has burned down to the proper distance there 
is introduced a charge of the iron ore mixed with flux 
(usually limestone) when the latter is necessary. Over this 
is placed a charge of fuel, then a second layer of ore and 



199 

flux, and so on in alternate layers until the f urnace is full. 
It is usually several months before a full charge is employed 
in a furnace. The principal steps in the reduction in a coke 
furnace may be outlined as follows. 

The hot blast from the tuyere pipes gives up its oxygen 
to the carbon of the fuel with which it first comes in contact 
producing carbon dioxide. The carbon dioxide is very 
quickly decomposed by the excess of red hot carbon forming 
carbon monoxide, so that at a very short distance (not over 
three feet from the tuyere pipes) no free oxygen or carbon 
dioxide are found in the ascending blast. At a short distance 
from the tuyeres the gaseous current is composed of about 
% carbon monoxide and % nitrogen. The nitrogen is chem- 
ically inert but the carbon monoxide has great reducing 
power and as it comes in contact with the descending heated 
iron oxide it removes the oxygen from the oxide leaving 
metallic iron and forming carbon dioxide. This change takes 
place in what is called the upper reducing zone of the furnace 
and may be approximately stated as embracing the upper 
third of the furnace. 

Just below this zone the carbon dioxide of the limestone 
is driven off. 

The lime, clay, sand, and other impurities of the gangue, 
together with the metallic iron and coke, continue the 
descent, growing hotter and hotter. In this descent below 
the upper zone the principal and most important action 
which takes place is the removal of some of the carbon from 
the gaseous carbon monoxide with the production of carbon 
dioxide and the formation of iron carbide or cast iron. 
When the material of the furnace has descended to the level 
a little above that of the tuyere pipes a temperature is 
reached at which the silica reacts upon the lime and other 
bases, producing a slag composed of fusible silicates. It is 
in this region of the furnace that the oxides of silicon, sul- 
phur, and phosphorus are reduced and these bodies enter 



•200 

into the iron. The iron itself here reaches the fusing point 
and the entire charge is fused and flows down into the 
hearth, settling in two layers beneath the tuyere pipes, the 
slag on top. The region in which the oxides of silicon and 
phosphorus are reduced and the changes just referred to 
take place, is frequently called the lower reducing zone. For 
convenience in description we shall call the region between 
the upper and lower reducing zones the neutral zone. 

There is an upper tap hole through which the slag is 
allowed to run off and the iron is drawn orf at the lower hole 
at stated intervals. The slag, which has about six times the 
bulk of the iron, is made to run off to the most favorable 
point for removal from the vicinity of the furnace. The iron 
runs out into sand or iron moulds, forming rough cylindrical 
masses weighing about 100 pounds (called pigs) and the 
term pig-iron, as generally used, is synonymous with cast 
iron. The changes which take place in the different parts of 
a coke furnace may be summarized as follows: assuming the 
iron ore to be magnetite, this being the form to which all the 
ores pass soon after entering the furnace, then in the upper 
reducing zone the reaction is Fe s 4 — 4CO=Fe 3 — 40O 2 ; in the 
neutral zone it is Fe 5 — 2CO=Fe 5 C— C0 2 : between the tuyeres 
and the lower reducing zone the reactions are C0 2 — C=2CO 
and C-0 2 =C0 2 . 

The description above given for reducing ores applies to 
a modern coke furnace. "W lien other fuel is used the shape 
and dimensions of the furnace are usually different and the 
reactions occurring in the furnace are somewhat differently dis-' 
tributed. By the use of selected ores and fuel and by special 
treatment in particular furnaces the nature and quality of 
the iron is under considerable control. 

En the neutral zone as above designated it is pretty well established 
that the metallic iron takes oxygen from some of the carbon nonoxide 
forming iron oxide and depositing solid carbon. At the high tempera- 
ture of the lower reducing zone the solid carbon takes an active part 
in reducing the oxides of silicon, sulphur, and phosphorus. Some able 



201 

authorities assign much importance in this lower zone to the reducing 
action of the metallic cyanides which are known to be formed in the 
vicinity of the tuyere pipes. 

Slag and Fluxes. All ores contain more or less extrane- 
ous matter and it would be impossible to separate the iron 
from these impurities unless they were brought to a liquid 
state. The extraneous matter after fusion constitutes the 
slag-. If the impurities of the ore are not of such material as 
will fuse at the temperature of the furnace other materials 
are added to bring" about this result; the added material is 
known as flux. The principle which governs the addition of 
the flux is that complex silicates are more readily fusible 
than simple ones. If the natural matter accompanying the 
ore usually called gangue, be clay (silicate of aluminum) 
limestone is added as a flux. This provides for the forma- 
tion at the temperature of the furnace of a double silicate of 
calcium and aluminum which is more fusible than clay. If 
the gangue be silica, both clay and limestone are 
added the object being in each case to form fusible 
double silicates of aluminum and calcium. When silica is 
in excess in the slag there is too great a loss of iron by the 
formation of iron silicate. 

It may in general be stated that for each ton of iron pro- 
duced there is also a ton of slag and the bulk of the slag is 
about six times that of the iron. It thus becomes a serious 
problem in many places, to dispose of the slag produced at 
the furnaces. The slag is removed from the furnace in the 
most expeditious way and this of course depends upon the 
location of the furnace. It is often drawn off into bogies or 
trucks running on rails, the trucks being so arranged that 
the blocks of slag are easily removed when solidified. In 
this country at some furnaces side-tipping ladles lined with 
fire-brick are used to receive the slag, the ladle being 
mounted on trucks. With small furnaces the slag is usually 
run off into rough sand moulds from which it is removed 
when sufficiently cool. 



202 

Uses of the Slag. Slag lias been used for macadamizing 
roads, especially when suitable stone is not readily obtain- 
able, and for ballasting railways. Cast into blocks it has 
been used for break-waters, and occasionally for foundations 
of light structures; certain slags cast under proper con- 
ditions, have been used for paving blocks and for brick. 
The granulated slag which is produced by allowing melted 
slag to trickle into water, makes a good brick when mixed 
with tV its weight of lime and pressed into shape. The 
granulated slag ground to fine powder and mixed with lime 
yields an hydraulic cement. Slag wool or mineral wool is 
produced by blowing the melted slag with a jet of steam; 
this mineral wool is non-inflammable and a non-conductor of 
heat. The utilization of the slag is conducted on a large 
scale in Germany both in the production of brick and 
cement. In 1892 there were reported in that country ten 
slag-cement factories with a total production of 600,000 tons 
of cement. The slag run off from all the American furnaces 
during some of the most prosperous years would cover an 
area of a square mile to the depth of eight feet. 

Furnace Gases. The gases which are led off from the 
top of the furnace through the "down comer" pipes besides 
being hot are highly inflammable. They consist of nitrogen 
(amounting to something over % by volume), carbon tionox- 
ide (about % by volume), and carbon dioxide (about | by 
volume). These gases are conducted off and used as a 
source of heat for generating power, or more generally for 
heating the air which is to be fed to the furnace. For 
the latter purpose the escaping gases from the blast fur- 
nace are conducted into suitable " stoves " or furnaces where 
the proper amount of air is admitted for the combustion of 
the carbon monoxide. The best modern "stoves" may be 
said to consist of a closed chamber containing a volume of 
brick-work so arranged as to expose a large absorbing sur- 
face to the heated gases. When the absorbing material of 



203 

the " stove" has become heated the furnace gases by suitable 
valves are shunted to another "stove," while the air to feed 
the furnace is driven through the first. The air to feed the 
blast furnace absorbs the heat given out by the gases which 
have already passed through the furnace. In this way the 
temperature of the blast can be raised to the desired extent. 
The blast frequently enters the tuyeres at a temperature of 800 
or 900° C. and under a pressure of from five to twelve pounds. 
Some of the best chambers used to heat the blast contain brick so 
piled as to expose as much surface as possible— the Whitwell "stove" 
is divided by a series of partition walls in close proximity, built of fire- 
brick. The gases in their transit through the " stove " pass one wall at 
the top and the next at the bottom. In the Cooper "stove " hexagonal, 
honeycombed brick are stacked so as to make many flues through 
which the hot gases and air alternately pass. 

These " stoves" may be used to heat gaseous fuel as well 
as the air for itg combustion, when such fuel is employed. 
Gaseous fuel is preferred for certain operations in a manner 
similar to that for preparing water gas and by the incom- 
plete combustion of carbon; such gaseous fuel is generally 
known as "producer gas" and consists mainly of carbon 
monoxide. When the producer gas and air for its combus- 
tion are both raised in temperature by passing through the 
rt stoves " and the " stoves " themselves heated by the products 
resulting from the combustion, it constitutes the system of 
"regenerative firing" and very high temperatures can be 
obtained. 

From the above description it will be observed that the blast 
furnace is fed at the top with solid material, ore, flux and fuel, which 
form a continually descending column. It is fed at the bottom with air 
which continually passes upward in an ascending current. The total 
weight of the ascending current is about the same as the descending 
column. Some of the larger American furnaces use in 24 hours, 550 tons 
of ore, 450 tons of coal, 150 tons of limestone, and over 1000 tons of air. 
Such furnaces yield about one ton of iron for each ton of fuel. 

COMPOSITION AND PROPERTIES OF CAST IBON. 

•The iron direct from the blast furnace is often designated 
as pig-iron; after remelting it is called cast iron. This dis- 



204 

tinction is that of the foundry and not that of the laboratory. 
Chemically pig-iron is a particular variety of cast iron. 
Average cast iron contains from 90 to 95 per cent of iron, and 
from 2 to 5 per cent of carbon the remaining" constituents 
generally being silicon, sulphur, phosphorus, and manganese 
— the silicon being the most abundant of these. Of these 
ingredients of the cast iron the carbon and sulphur are 
derived from the fuel, the silicon, phosphorus, and man- 
ganese from the ore. 

There are two varieties of cast iron generally distin- 
guished, viz. : white and grey. These varieties are based upon 
the condition of the carbon present in the solid metal. Fused 
iron dissolves and chemically combines with the carbon and 
if all or nearly all of the carbon is retained in combination 
after solidification, the metal has an almost silvery fracture 
and is known as white iron. On the other hand if a portion 
of the carbon separates from the iron on cooling in the form 
of minute graphitic like crystals, the metal will have a dark 
grey color due to the separated carbon — this form is the grey 
iron. A variety intermediate between these two is called 
mottled iron. 

The difference of condition of the carbon in the white and 
grey iron is shown when specimens of each are dissolved in 
dilute sulphuric or hydrochloric acid. In the grey iron the 
separated carbon remains unaltered while in the white the 
constituent carbon passes off in combination with hydro- 
gen giving some of the hydro-carbons having a disagreeable 
odor which is often observed when white iron is acted 
upon by acids. 

The properties of the two varieties of iron are very dif- 
ferent. The white iron is slightly heavier, is much harder, 
and fuses at a much lower temperature. The grey iron is 
soft enough to be cut in a lathe, and is more fluid when fused 
than the white and is therefore better for casting. 

The condition of the carbon in the iron depends partly 



205 

upon the rate of cooling of the melted metal and partly upon 
the proportions of the other constituents present. Pure iron 
fused in contact with carbon is capable of combining with 
nearly five per cent of that element, but the amount of car- 
bon that will be taken up depends upon the other constit- 
uents of the fused iron. Manganese increases the amount of 
the carbon dissolved by the iron while silicon and sulphur 
decrease the amount. In the cooling of the melted iron, 
manganese and sulphur tend to prevent the separation of 
graphitic carbon while silicon tends to cause this separation, 
accordingly white iron usually contains less silicon than 
grey. 

If sulphur and manganese be present in the melted iron, it will 
more likely solidify as white iron. The effects of the manganese and 
silicon are the same both upon the melted and cooled metal but the 
sulphur tends to prevent the combination of the carbon with the 
melted iron and to cause it to combine with the solid iron. Phos- 
phorus is thought to prevent the separation of graphite but to a less 
extent than sulphur. 

The condition of the carbon in the solid iron can be 
materially modified by the rate of cooling. Rapid cooling 
prevents the separation of the carbon from the iron and slow 
cooling favors the separation, the first accordingly promotes 
the production of hard white iron and the latter that of grey 
iron. Chill-casting is brought about by virtue of the fore- 
going facts. Objects cast of soft grey iron may thus be 
made very hard externally by rapid cooling. If any partic- 
ular portion of a casting is required to be hard the corre- 
sponding part of the mold is made of a good conducting 
material so as to rapidly cool that part. When white cast 
iron is melted and cooled very slowly it becomes grey. 

The varieties of cast iron, of course, grade into each other 
and it is difficult in every case to specify the variety to which 
a specimen belongs. For commercial purposes there arc 
several grades of cast iron, the dark grey being number 1 
and the hardest white iron being number 8. 



206 

Cast iron is the most fusible variety of iron. It is neither 
malleable nor ductile nor can it be tempered. It is hard and 
brittle, as already stated; it may contain as much as 7 per 
cent of other elements. Its tensile strength is small as com- 
pared with wrought iron and steel and its application for 
constructional purposes is much more limited than these 
latter. The white iron is generally used for conversion into 
malleable iron and the grey iron for foundry iron. 

Wrought Iron. Wrought iron may be defined as commer- 
cially pure iron — it is not chemically pure as it contains 
something less than .15 per cent of carbon, with minute pro- 
portions of sulphur, silicon, and phosphorus. 

Manufacture of Wrought Iron. Wrought iron is now 
made by two processes, 1st. By the direct process, that is 
directly from the ore; 2nd. By the indirect process, that is 
by the purification of cast iron. The indirect method is that 
most generally followed and will be first described. The 
principle of the more common process known as the pud- 
dling process will be given first. 

Puddling. The puddling process is conducted in a re- 
verberatory furnace in which cast iron is subjected to a 
purifying process, the carbon, phosphorus, sulphur, silicon, 
&c, being oxidized and removed. The general form of the 
furnace used is shown in the figure, the operation being con- 
ducted as follows : The bottom and sides of the furnace bed 
are covered with "fettling" consisting of slags rich in iron 
silicate or with such slags mixed with iron oxide. Five or 
six cwt. of pig-iron are charged into the furnace, the doors 
closed and the draughts turned on. When the iron is 
melted it is well rabbled or stirred so that every part of it is 
brought into contact with the oxide. Very soon the iron 
boils violently in consequence of the escape of carbon 
monoxide. After the boiling stage the metal "drops" or 
comes to "nature" and the whole mass becomes pasty. Slag 



207 

or tap-cinder is drawn off during and at the end of the 
operation. 

The silicon, manganese, and phosphorus are separated 
mainly during the melting stage and pass into the slag. 
During the boiling of the iron the carbon is removed and 
also a further portion of phosphorus. The sulphur is 
eliminated in the slag in the form of iron sulphide. 

The pasty iron is balled up by the puddler into masses 
weighing from fifty to one hundred pounds which are 
removed from the furnace and subjected to the action of a 
steam hammer. The hammering presses out the slag and 
causes the pasty particles of iron to cohere forming an 
oblong mass or "bloom." The "bloom" is passed through 
rollers and pressed into "puddled bars" but these bars are 
not yet fit for use. The puddled bars are cut up and made 
into bundles, reheated in the mill furnace, withdrawn at the 
welding heat, and passed through rollers until required 
dimensions are obtained. By this operation the texture of 
the iron is made more uniform, a fibrous structure imparted, 
and the quality generally improved. This product is com- 
monly known as merchant bar. If the merchant bar be 
doubled upon itself, heated and rolled, it gives the "best iron 
bar" or wire iron. These operations improve the quality of 
the iron by pressing out more of the slag and appear to pro- 
duce a slight chemical effect by removing by oxidation some 
of the impurities of the iron. 

In the puddling operations just described the impurities 
of the cast iron are oxidized mainly by the oxide of iron used 
in the hearth though the oxygen of the air exerts some 
action and it is quite customary to add a little iron oxide or 
a mixture of iron and manganese oxides with the charge or 
after the metal has been melted. These also take part in the 
oxidation of the impurities. These puddling furnaces were 
originally lined with siliceous material but experience has 
led to the basic lining. 



208 

In this puddling process grey pig-iron is used because it 
becomes more liquid when fused. It is often spoken of as 
the pig-boiling process because the metal is so thoroughly 
liquefied and presents the appearance of violent boiling 
when the carbon monoxide is escaping. The whole opera- 
tion usually occupies from one and a quarter to one and a 
half hours. 

The puddling" process was formerly and is yet sometimes preceded 
by a refining process. The refining consists essentially in subjecting 
the fused metal to a draught of air by which a portion of the iron is 
oxidized. The iron oxide reacts upon the impurities of the iron largely 
removing the silicon and sulphur and some of the phosphorus. The 
refined iron then remaining is puddled upon the hearth of a reverbera- 
tory furnace almost entirely similar to that used fn the pig-boiling pro- 
cess. Formerly the impurities of the refined iron were oxidized largely 
by the oxygen of the air and the iron did not become liquid as in the 
pig-boiling process. It was therefore known as dry puddling. In dry 
puddling iron oxide latterly came into use to assist in the oxidation of 
the iron. The refining and dry puddling of the iron is not now gen- 
erally practiced . 

Mechanical Puddling. Owing to the heavy manual labor 
involved in the puddling operations described and to the 
desire to cheapen the process, several attempts have been 
made to effect mechanical puddling. 

Dank's rotating puddling furnace (an American inven- 
tion) was one of the most successful of these. The puddler 
consists of a large cylinder arranged to rotate about its hori- 
zontal axis. The inside of the cylinder is lined with "fettling," 
iron oxide, and lime. The flame gases from the heating 
furnace enter the cylinder at one end and pass out at the 
other. The cast iron to be puddled is run into the cylinder 
in a liquid state and the puddling is accomplished by rotating 
the cylinder by mechanical means. The results reached are 
brought about by the same chemical actions described in the 
pig-boiling process. This furnace has been gradually aban- 
doned both in this country and Europe and is no longer in 
general use. 



209 
WROUGHT IRON DIRECT FROM THE ORE. 

The earliest wrought iron was undoubtedly obtained 
direct from the ore and bar iron is still to a limited extent 
obtained in the same way. In these early methods the ore 
was heated in contact with the fuel under the action of the 
simple blast — in India to-day this method is followed, the air 
being blown in with a hand bellows. The American bloomery 
process is another example of a direct reduction process. 
The powdered ore mixed with charcoal, is heated on the open 
hearth of a bloomery furnace fed by a blast. In the pro- 
cesses just mentioned and in nearly all the direct processes 
the fuel used is charcoal. The methods as a rule are expen- 
sive and can only be followed where fuel and labor are cheap 
and special ores are accessible. 

Eames' Process. Among the most recent methods of 
making bar iron may be mentioned that of Eames or the 
process of the Carbon Iron Company. In this process the 
iron ore is deoxidized in a reverberatory furnace which has a 
hearth lined with graphite or graphite mixed with some iron 
oxide. The iron ore is mixed with coke which has been 
treated with milk of lime (retarded coke) to diminish ten- 
dency to oxidation and placed upon the hearth of the furnace. 
The furnace is heated by natural gas and the reduction takes 
place at a moderate temperature. 

When the ore is reduced the spongy metal is worked into 
balls and afterwards rolled into bars ; or it may be charged 
while still hot into a bath of melted pig-iron on the open 
hearth of a steel furnace and ultimately converted into steel. 
This process has given satisfactory results in Pittsburgh and 
has passed to the commercial scale. 

There are many other processes that have succeeded hi 
obtaining iron direct from the ore but the Eames and the 
American bloomery process are the most important now- 
operated in this country. The Eames process has not yet 

been adopted in Europe. 
14 



210 

Properties of Bar or Wrought Iron. Wrought iron man- 
ufactured by the above described processes always contains 
some carbon and usually some silicon, phosphorus, and some 
sulphur. Chemically pure iron has neither the hardness nor 
tenacity of the commercial bar iron. Unless the amount of 
sulphur in the iron is very small it produces brittleness in 
the iron when it is hot, called red-shortness. An excess of 
phosphorus produces brittleness at ordinary temperature or 
cold-shortness. 

The best wrought iron has a fibrous texture to which its 
tenacity is due. Such iron is very tenacious, ductile, and 
malleable. When the iron during its manufacture has not 
acquired the fibrous texture the strength is much less. Its 
strength is much greater in the direction of than across the 
fibres. It is thought that phosphorus in iron tends to cause 
large crystals preventing the fibrous texture and weakening 
the iron. The texture of iron is believed to have sometimes 
changed, gradually becoming granular and crystalline by 
frequent or long continued vibration. 

At a red heat it becomes pasty and can then be readily 
welded and easily fashioned into shape. The smith usually 
sprinkles the heated metal with sand or borax to remove the 
oxide before hammering the surfaces to be welded together. 
The use of wrought iron for structural purposes, ship-build- 
ing, armor plates, bridge construction, &c, has now been 
largely replaced by that of steel. 

Manufacture of Steel. Steel in general contains more 
carbon than bar iron and less than cast iron. It is made 
either by purifying cast iron and then adding the necessary 
amount of carbon and other ingredients to form steel, or by 
adding carbon and other ingredients to bar iron. The first 
method is more generally employed in the manufacture of 
mild steel or ingot iron ; the second in the production of hard 
steel. 

The two principal processes in making steel from cast 




B 



i nrr|l »— 



n 



211 

iron are the Bessemer and Open Hearth processes. In the 
Bessemer process the decarbnrization and purification of the 
cast iron is accomplished by the oxygen of the air. In the 
Open Hearth process the oxidizing- agent is mainly iron 
oxide. 

The Bessemer Acid Process. In this process pig-iron 
melted in a cupola furnace or taken direct from the blast 
furnace is run into egg-shaped vessels known as "con- 
verters." The "converter" (fig. ) is externally of iron and 
is lined with acidic or siliceous material and is arranged so 
as to rotate upon trunnions fixed on either side. Below the 
bottom of the "converter" is a blast-box, and several holes 
% inch in diameter pass from the blast-box through the 
bottom of the "converter." The "converter" is turned into a 
horizontal position to receive the charge of from five to 
twelve tons of iron. The air blast is then turned on under 
a pressure of fifteen or twenty pounds and the " converter " 
rotated to an erect position. The air then passes up through 
the melted metal. The silica and manganese are then first 
oxidized with marked increase of temperature in the "con- 
verter;" then the carbon is oxidized to carbon monoxide 
which burns with a long flame at the mouth of the "con- 
verter." Some of the iron is also oxidized during the blow. 

The oxidized silicon combines with the oxides of iron and 
manganese and rises to the surface of the metal as a slag. 

When the carbon flame "drops" at the mouth of the 
"converter," it indicates that the operation is complete, that 
is, the carbon, manganese, and silicon have been removed 
from the iron. 

The purified metal is then converted into the desired 
quality of steel by the addition of spiegeleisen or ferro-man- 
ganese to the melted charge just before it is poured. The 
ferro-manganese is a cast iron rich in carbon and manganese 
and of well determined composition; the ferro-manganese is 
always added in a fused state. The metal is allowed to stand 



212 

a few minutes after the last addition and is then poured into 
ladles and east into ingots. The addition of the ferro-man- 
ganese not only gives the required hardness to the steel but 
the manganese counteracts the tendency to red-shortness. 

The above was the original process and it will be observed 
that the " converter" was lined with siliceous or acidic mate- 
rial. It was found that the process could only be applied to 
iron fairly free from phosphorus for this objectionable con- 
stituent was but little removed by the operation. 

The Bessemer Basic Process. The mechanical arrange- 
ments and general principles in the basic process are exactly 
the same as in that just described but the "converters" are 
lined with lime and magnesia (basic material) and lime to 
the amount of about 1-100 the charge of iron is put into the 
"converter" before the metal is run in. The "blow" is con- 
tinued a little longer than in the original process and the 
oxidized phosphorus combines with the lime and is removed 
in the slag. By this modification in the original process it 
has become applicable to iron rich in phosphorus. The slag- 
produced in the basic process is rich in calcium phosphate 
and is very valuable in agriculture. The basic process now 
finds wide application. 

Open Hearth Steel. The Siemens-Martin process may be 
taken as typical of the open hearth methods. In the original 
method it was attempted to produce steel by melting together 
on the hearth of a reverberatory furnace cast and bar iron 
in the proper proportions. The method did not yield definite 
results and as now modified the Siemens-Martin process 
closely resembles in principle the original puddling process. 
The furnaces are similar to but larger than the puddling 
furnace and are lined with siliceous material. "When the pig 
iron to be decarburized is melted appropriate quantities of 
iron oxide are introduced into the furnace. By thorough 
stirring the carbon, silicon, &c, are oxidized and removed 



213 

from the iron, the oxidation being accomplished mainly by 
the oxygen of the iron oxide bnt in part by the oxygen in the 
flame used to heat the hearth. After eight or ten hours the 
operation is complete but as in the Bessemer process the 
metal would be too soft for use. The required steely char- 
acter is imparted to it by the addition of ferro-manganese to 
the metal as it is drawn off for casting. It is still customary 
in this process to add to the melted pig-iron waste scraps of 
bar iron and basic slag along with the iron oxide. 

With the acid lined furnace in this process the same dif- 
ficulty to a certain extent is experienced as with the acid 
Bessemer process; that is, to get the best results material free 
from phosphorus must be used. 

The basic lining has accordingly been adopted in this pro- 
cess the chief modification being the substitution of a 
working bottom of basic material for the siliceous bed. As 
in the basic Bessemer process some lime is introduced with 
the charge and the process has been successfully applied to 
the phosphorus ores with every prospect of great extension. 
The Siemens-Martin process is very generally operated by 
" regenerative firing" (page 203), by which high tempera- 
tures are produced and the purified iron easily kept perfectly 
liquid. 

The steel produced by the Eames method already referred 
to comes under the head of open hearth steel. 

There are numerous modifications of the open hearth methods but 
the essential principles of the most important have been indicated 
above. 

Cementation Process. Steel from Bar Iron; Hard or 
Tool Steel. The process of making steel from bar iron by 
carbonization is known as the cementation process. In this 
process bar iron imbedded in charcoal is subjected to the 
prolonged action of a high temperature. For this purpose 
bar iron of the best quality is cut into suitable lengths and 
placed in chests of fire-bricks. The chests are about ten or 



214 

twelve feet long, three to three and one-half feet wide and 
deep, and open at the top. 

The charge of each chest generally consists of from six to 
eight tons of iron and two chests are inclosed in the same 
furnace. Ground charcoal is spread upon the bottom of the 
chests and upon this bars of iron are laid in regular order, 
small intervals being left between adjoining bars (the bars 
are about four inches wide and a little less than an inch 
thick). Charcoal is then added until the open spaces are 
filled and the bars covered by a continuous layer; over this 
another layer of bars is placed and the operations repeated 
until the chests are full. A thick layer of carbon is placed 
at the top and the whole is covered with a thick layer of 
grinders' waste (wheel-swarf, silica and iron dust from the 
grinder's wheel) or similar material. This substance at a 
moderate heat becomes plastic and forms a perfect cover to 
the chests and prevents contact of air with the charcoal. 
The chests are generally placed in pairs in a dome-shaped 
furnace, the fire-place being below the chests and the flues 
passing up between and at the sides, the whole being covered 
by a cone-shaped chimney fig. The temperature is raised 

gradually until it is about 2000° F., at which point it is main- 
tained for a period of six or ten days, the time depending 
upon the quality of the steel required, the harder steel requir- 
ing the longer time. The progress of the operation is known 
by the appearance of trial bars, one of which is arranged in 
each chest so that it may be withdrawn when desired. When 
the operation is complete the bars are taken out and are 
found to have increased from one-half to one per cent in 
weight and are usually covered with hollow protuberances 
resembling blisters, hence the term "blister steel." Analysis 
shows that the increased weight is due to the combination of 
carbon with the iron and the carbon is found not only at the 
surface but also at the centre of the bars. 

The chemistry of the process is believed to be due to the 



215 

action of carbon monoxide npon the iron. It has been 
shown experimentally that soft iron at a low red heat is 
capable of absorbing* four times its volume of carbon monox- 
ide, the action of the iron upon the gas is thought to be 
indicated by the reaction Fex+2CO=Fe x C+C0 2 ; the carbon 
dioxide produced is reconverted into carbon monoxide by 
the charcoal, C0 2 +C=2CO. The carbon monoxide is pro- 
duced in the first instance by the action of the small amount 
of atmospheric oxygen present in the chest upon the carbon. 
The carbon monoxide absorbed by heated iron is retained 
unchanged unless the temperature of the iron be raised 
above a red heat. % 

Shear Steel. Though carbon is found throughout the bars 
of the above described steel, it is more abundant nearer the 
surface, while below the surface are found numerous blister 
cavities. To render the steel more homogeneous and improve 
its quality much of it is subjected to a process of fagoting. 
The bars are broken, piled, heated, and forged into shape under 
the tilt-hammer as is the case with bar iron. One heating and 
welding constitutes single shear steel. The density, tenacity, 
malleability, and ductility of the steel are greatly increased 
by fagoting and such steel is suitable for the manufacture of 
certain kinds of tools, woolen shears being among them, hence 
the name shear steel. The fagoting operation repeated upon 
the single shear steel produces double shear, the latter again 
being superior to the single shear for certain purposes. 

Crucible Steel; Cast Steel. The best steel for tools and 
for many other purposes is produced by melting blister steel 
in crucibles usually clay or plumbago. 

The blister-bars are broken into fragments and a charge 
from fifty to one hundred pounds introduced into the crucible. 
The fusion is accomplished in a wind furnace, the surface of 
the metal being protected from oxidation by covering it with 
some fusible silicate or other flux. The fused contents of the 



216 

crucibles are poured into the moulds and when heavy ingots 

or castings have to be made the contents of several crucibles 

are poured into the same mould; sometimes this is done 

directly but generally in large castings the metal is poured 

from crucibles into a receiver and from that into the mould. 

The cast steel is more homogeneous than the shear steel and 

is used to make the finest cutlery. 

Crucible steel is, apparently, justly thought better than that froni 
other sources (Siemens and Bessemer). The cost of crucible steel limits 
its production to that of high quality for cutting instruments, for 
springs, for fire-arms, &c. Other material than blister bars is used for 
the production of crucible steel but even then the product is thought 
inferior to that from the former source. It is often found advantageous 
in crucible steel for special purposes to introduce some manganese. 
Small quantities of chromium, tungsten, silicon, nickel and titanium 
also appear to have beneficial effects upon steels desired for certain 
purposes. 

Case -Hardening. Small objects which require the ex- 
ternal hardness of steel can be made of bar iron and then 
hardened externally by heating them in contact with carbon- 
aceous matter and afterwards cooling suddenly — this process 
is known as case-hardening. The reverse process to this 
consists in heating articles made of cast iron in contact with 
oxide of iron or other suitable oxidizing agent by which they 
are converted into malleable cast iron. In case-hardening car- 
bonization is effected, in the reverse process decarburization. 

Distinction between Steel, Cast and Bar Iron. Properties 
of Steel. These varieties of metal grade so imperceptibly 
into each other that it is impossible to classify them by any 
definition that will cover all the uses of the terms. The 
following distinctions are generally applicable — cast iron 
contains the greatest amount of carbon and is not malleable ; 
steel is malleable and can be hardened by sudden cooling 
from high temperature ; bar iron is malleable and can not be 
hardened by sudden cooling. Mild steel or ingot iron in- 
cludes all the varieties of refined iron except the softest bar 



217 

iron and the hardest steel, that is all the refined iron made 
by the processes involving" complete fusion (open hearth and 
Bessemer). Bar iron is pig-iron refined without complete 
fusion. 

Steel is hardened hy sudden cooling from a high temper- 
ature and it is usually done by plunging it into oil or water. 
It is tempered by reheating the previously hardened steel but 
not so highly as before, and cooling more or less suddenly. 
It is annealed by reheating the hardened steel and cooling 
slowly. After the first operation steel is hardest and most 
brittle, after the third it is softest and toughest, and after the 
second it is in an intermediate condition. The foregoing 
terms are not always used in the sense here given. 

The mild steels have nearly entirely replaced bar iron in 
structural works. Steel has also displaced iron in armor 
plates in war vessels. The qualities of steel for this latter 
purpose have been greatly improved both by the foundry 
treatment of the large masses and by the addition of a small 
per cent of the other metals; the most important alloy being 
that with nickel, which is used in the celebrated Harvey 
process. 

Chemical Properties of Iron. Pure iron is not acted upon 
by dry air at the common temperature. At a red heat it 
oxidizes and will burn at a white heat, in both cases forming 
the black oxide. The finely divided metal obtained by reduc- 
ing the red oxide with hydrogen takes fire spontaneously 
when exposed to the air. At a red heat iron decomposes 
water with the liberation of hydrogen. 

Pure water at the common temperature does not tarnish 
the surface of iron but the combined agency of water and 
carbon dioxide produces rusting which results from the 
formation of hydrated sesquioxide, 2Fe20 3 ,3H L .0. In the 
action the carbonate is first produced and this is dissolved 
by the carbonic acid, the dissolved carbonate is decom- 
posed by the oxygen of the air and converted into the hy- 



218 

drate (Fe+H 2 0+C0 2 =FeC0 3 +H 2 and 4FeCO s +0 2 +3H 2 = 

2Fe 2 3 ,3H 2 0+4C0 2 ) This reaction explains why the rusting of 
iron is so greatly facilitated by acid vapor. The stains so 
frequently observed to proceed from an iron nail are diffused 
by the formation and solution of the carbonate and sub- 
sequent conversion of it into the hydrate or other insoluble 
form; wet linen in contact with a nail is very soon thus 
stained. 

Dilute sulphuric, nitric, and hydrochloric acids act readily 
upon iron but the two acids first named have no perceptible 
action when concentrated. 

Iron forms two classes of compounds, the ferrous and 
ferric — in the first it is a dyad, in the second it may be 
regarded as a triad or tetrad. 

Iron Oxides. There are three oxides of iron, FeO, Fe 2 3 , 
and Fe 3 4 . 

Iron Monoxide; FeO. This is a powerful base and readily absorbs 
oxygen passing to Fe 2 3 . It is not found in the free state but can be 
artificially produced by careful manipulation. 

Sesquioxide of Iron; Ferric Oxide; Bed Oxide ; Fe 2 0%. This 
oxide is a weak base and is isomorphous with alumina. It 
occurs abundantly in nature as specular iron ore of which 
there are many varieties. The artificial sesquioxide is fre- 
quently used as a red pigment under the name of Venetian 
red. For this purpose it is prepared by decomposing the 
ferrous sulphate by heat. The hydrated sesquioxide con- 
stitutes the brown haematite or limonite ore. 

The sesquioxide and its hydrate are the common coloring 
matter of the soils. Its presence in the soils favors the 
decomposition of organic matters by supplying oxygen to 
them. In this action the ferric oxide is reduced to the fer- 
rous, this latter then combines with the oxygen of the air 
and reforms the ferric oxide. This operation is continually 
repeated, the ferrous oxide acting as a carrier of oxygen 
from the air to the decomposing body. When the ferric 



219 

oxide is heated to whiteness or in a reducing flame it loses 
oxygen and passes to the tetroxide. 

Triferric Tetroxide; Magnetic Oxide; Black Oxide; Fe/M. 
This oxide occurs abundantly in nature and is one of the 
chief ores of iron. It is always produced when iron is oxi- 
dized at a high temperature. It is a very stable compound 
which fact has led to its use as a covering to protect against 
rust. In the Bower-Barff process the metal heated to red- 
ness is subjected to the action of steam by which it receives 
a dense film of the oxide. The same result is obtained by 
subjecting the heated metal to the action of the carbon 
cLL monoxide and air. 

Iron Carbonate; Spathic Ore; Siderite; FeC0 3 . The car- 
bonate occurs abundantly in nature and is a valuable ore of 
iron. It is often associated with the carbonates of calcium, 
magnesium, and manganese, with which it is isomorphous. 
It is often found in natural waters, being soluble in water 
containing carbon dioxide. Mineral springs containing the 
carbonate in solution are called chalybeate springs. For 
reasons already explained these waters usually deposit the 
hydrated oxide when exposed to the air, hence the rusty 
deposit which always occurs about such springs. 

Ferric Sulphide; Iron Pyrites; FeS 2 . This is the most important 
sulphide and occurs widely and abundantly in nature. It is sometimes 
used as an ore of iron but more generally as an ore of sulphur. It is 
generally known under the name of pyrite or iron pyrites. There are 
two other* sulphides of iron, FeS and Fe 3 S 4 . The first is used in the 
laboratory for making hydrogen sulphide and is itself prepared by 
heating iron filings and sulphur together. The Fe 3 S 4 occurs in nature 
under the name of magnetic pyrites. 

Ferrous Sulphate; Copperas; Green Vitriol; FeS0 4 , Aq. 

Ferrous sulphate is obtained in large quantity as a bye-pro- 
duct in the manufacture of alum. It is made directly in 
large quantity by dissolving scrap iron in warm sulphuric 
acid, evaporating and crystallizing. It is also made by oxi- 



220 

dizing the burnt pyrites left in the manufacture of sulphuric 
acid. 

The salt crystallizes in green crystals which are usually 
tinged with a yellowish white, due to the presence of ferric 
sulphate. Ferrous sulphate is largely used in dyeing, tan- 
ning, and in the manufacture of inks, Prussian blue, 
Venetian red, and other pigments. It is a great e sidizing ^dum 
agent and because of this power it is used to precipitate gold 
from solution and will reduce indigo to the soluble con- 
dition. 

There is a number of other sulphates of iron the most important 
of which is the ferric sulphate Fe 2 (S0 4 ) 3 . It has been found in nature 
and can be produced artificially. Solutions of this salt mixed with 
solutions of potassium and ammonium sulphates produce iron alums. 

Other Compounds of Iron. Iron forms two chlorides, ferrous and 
ferric ; the solution of the first is used medicinally and that of the 
second for disinfecting. It forms two iodides corresponding to the 
chlorides. It also forms ferrous and ferric phosphates and nitrates and 
a number of other inorganic compounds too numerous and unim- 
portant to be considered here. 

Reactions of Iron Salts. Ferrous Salts. By the addition of 
caustic alkaline solutions or ammonia, ferrous salts give 
white precipitates, rapidly changing to green and brown. 
Carbonates of potassium, sodium, and ammonium give white 
precipitates which change to yellowish brown. Hydrogen 
sulphide gives no precipitate. Ammonium sulphide (NH 4 ) 2 S 
precipitates black iron sulphide soluble in acids. Potassium 
ferri-cyanide gives a deep blue precipitate. 

Ferric Salts. These give Prussian blue precipitate with 
potassium ferrocyanide and intense blue-black with infusion 
of nut-galls (gallo-tannic acid). 

COBALT. 

Cobalt occurs in nature often associated with nickel. Its chief ores 
are the arsenide and sulphide. Cobalt is magnetic like iron and closely 
resembles iroD in other properties. The metal has found no applica- 
tion except to a small extent in plating, as with nickel. This is 
accomplished by the electrolysis of a solution of the double sulphate of 



221 

cobalt and ammonium. The deposit is harder, more tenacious, and of 
greater beauty than nickel. It has been termed superior nickel plating. 

Useful Compounds of Cobalt. Several cobalt compounds are of 
considerable importance in the arts being used to produce permanent 
and brilliant colors. Some of the most important of these are smalt, 
Thenard's blue or ultramarine. 

Smalt. Smalt is a blue pigment very extensively used in the arts. 
It is a potash glass colored with the oxide of cobalt and consists of a 
mixture of the silicates of potassium and cobalt and sometimes other 
metals. It is used in painting on porcelain, in making stained window 
glass, in making tiles, and as a blue pigment. 

ThenarcVs Blue; Cobalt Ultramarine. This pigment consists of 
alumina colored with the oxide or phosphate of cobalt. It is used both 
as a water and an oil color. There is a number of other permanent 
pigments prepared from the compounds of cobalt. 

Cobalt Chloride. This salt is a basis of one of the sympathetic 
inks. A dilute solution of the chloride has a faint rose color which is 
not visible on paper but turns blue upon drying, due to loss of water 
of crystallization ; it disappears again upon cooling due to absorption 
of atmospheric moisture. 

NICKEL. 

Nickel resembles iron and cobalt in many of its proper- 
ties. It is malleable and dnctile and next to manganese it is 
the hardest of the metals. It is magnetic, like iron and 
cobalt and occurs nearly always in meteoric iron. The ores 
of nickel are found in numerous places throughout the world 
but are generally very complex, usually being associated 
with a number of other metals. 

Nickel is largely used for coating iron and other bodies 
by electrolysis, a solution of the sulphate being used for the 
purpose. It is made into crucibles and dishes, for use in the 
laboratory. It is used for coin and for making various 
alloys. Alloyed with copper and zinc it forms German 
silver. The alloy of nickel with steel very greatly excels the 
steel in the important qualities required in armor plates. 
Processes have been devised for rolling nickel into thin 
sheets, and these can be welded to iron and steel plates. 
Pure nickel resists the action of the atmosphere and both 
fresh and salt water almost as well as the precious metals. 



222 

MANGANESE. 

Manganese is not used in the metallic state. It resembles iron in 
many of its properties and its ores are often found associated with 
those of iron. It occurs in nature in many forms but its principal ore 
is Pyrolusite, Mn0 2 . 

Pyrolusite ; Mn0 2 . This oxide is largely used in the preparation of 
chlorine and oxygen and in the manufacture of glass ; it is also the 
source of the other compounds of manganese. 

Other Oxides of Manganese. The higher oxides of manganese are 
acidic ; Mn 2 3 and Mn 2 7 . The latter in contact with water produces 
permanganic acid, H,Mn 2 8 . This acid and its alkaline salts are pow- 
erful oxidizing agents. By virtue of this property potassium per- 
manganate finds application in the laboratory and is used as a 
disinfectant. Condy's disinfecting fluid being composed of it. The 
sodium permanganate generally displaces it as a disinfectant it being 
the cheaper. 

Ferro=Manganese ; Spiegeleisen. These bodies are alloys of iron 
and manganese rich in carbon. The first is the richer in manganese. 
Both Spiegeleisen and ferro-manganese are largely used in the manu- 
facture of Bessemer and Open Hearth steel. 

CHROMIUM. 

Chromium in the metallic state finds no useful application. Some 
of its compounds are largely used in the preparation of pigments. It 
derives its name from the Greek word xp&w because of the color of its 
compounds. Chromium is generally found in nature as an oxide in 
combination with iron oxide. Its alloys with iron are important. The 
presence of chromium in iron or steel increases the tenacity, hardness, 
and elasticity and gives finer texture. 

Important Compounds of Chromium. The compounds of chromium 
most used in the arts are chromates, compounds in which the chro- 
mium oxide takes the part of an acid radical. These chromates are all 
made directly by the oxidation of the chrome iron ore (FeO, Cr 2 3 ). 

Potassium chromate and bichromate are thus made, the latter 
K 2 Cr 2 7 in large quantities, and other compounds of chromium are 
derived from them. 

Potassium bichromate is used in the preparation of nearly all 
chrome pigments, and in the production of a variety of colors in dyeing 
and calico printing. It is a powerful oxidizing agent and is used in the 
manufacture of safety matches and as a source of oxygen for organic 
analysis. It is readily reduced by organic matter and is an agent 
frequently employed in testing the purity of water. Mixed with gela- 
tine and exposed to the light it is reduced and the gelatine rendered 



223 

insoluble. This fact is taken advantage of in photography and is the 
basis of the carbon process. 

Lead Chromate; Chrome Yellow, and Orange Chrome. The lead 
chromate constitutes two of the most important chrome colors, 
chrome yellow and orange chrome. Chrome yellow is the normal 
chromate of lead (PbCr0 4 ), and is prepared by bringing together in 
solution lead acetate and potassium chromate. It is largely used in 
painting and in calico printing. Orange chrome is the basic chromate 
of lead (PbCr0 4 , PbO) and may be obtained by boiling the normal 
chromate with lime by which a portion of the acid is removed. Stuffs 
made yellow with the normal chromate may be made orange by a 
bath of lime water. 

There are many other chrome colors which are of great permanence 
and have many applications. 

MOLYBDENUM, TUNGSTEN, AND URANIUM. 

The metals molybdenum, tungsten, and uranium are not used in the 
metallic state. Their compounds have been but little studied and are 
not of great importance. 

Like chromium they all form acid oxides. 

The compounds of molybdenum find no useful application in the 
arts, but some of them are useful as special reagents in the laboratory. 

Tungsten alloyed with steel in certain proportions improves its 
properties in several respects and such alloy is used in the preparation 
of certain tools. Sodium tungstate is used as a mordant and muslin 
steeped in a solution of this salt will not burn with a flame. Some of 
the tungstates are used to a certain extent in the preparation of pig- 
ments. The tungstate of calcium has found recent application in 
forming a fluorescent surface for detecting the Roentgen rays. 

The oxides of uranium are valuable for glazing porcelain black and 
sodium uranite is prized for painting and staining glass under the name 
of uranium yellow. 

BISMUTH AND ANTIMONY. 

Bismuth. This metal is found native in small quantities in widely 
distributed localities. In the metallic state it is used only for the con- 
struction of the electric thermo-pile, being too brittle for other use. 
Bismuth is chiefly used in the preparation of alloys. It usually confers 
hardness and fusibility upon the alloys and causes them to expand in 
solidifying. 

Fusible metal is an alloy of two parts of bismuth, one of tin. ami 
one of lead. This alloy fuses below 180° C. though the fusing point of 
tin, the most fusible of the three, is much above this. An alloy of three 
parts of lead and two of bismuth has ten times the hardness and 
twenty times the tenacity of lead. An alloy of lead, tin. and bismuth 



224 

is largely used for the electrotyping process, it is very fusible and takes 
a fine impression of the mould. 

Compounds of Bismuth. The oxicle of bismuth (Bi 2 3 ) is used to a 
limited extent for glass and porcelain staining. Bismuth nitrate is 
largely used medicinally and also as a colorless flux for certain enamels. 
The oxy chloride of bismuth is used to a limited extent as a pigment 
under the name of pearl white. 

Antimony. Antimony like bismuth is too brittle for use in the 
metallic state. Its only application as a metal is the construction of 
therm o-piles in conjunction with bismuth. Antimony forms valuable 
alloys. It generally increases the fusibility, hardness, and brittleness 
of the metals and confers the property of expanding upon solidifica- 
tion. It is accordingly one of the constituents of type-metal, lead being 
the other. The same metals with tin are used for stereotype plates. 
With nine-tenths tin it forms Britannia metal. The number of useful 
alloys of this metal is large. 

Important Compounds of Antimony. Antimony sulphide, Sb 2 S 3 . 
This sulphide is used in the preparation of safety matches and is fre- 
quently one of the constituents of the friction tube composition used in 
firing cannon. It gives a bluish white flame with nitre and is used in 
pyrotechny. This sulphide roasted in air and largely converted into 
the oxide is used for coloring glass yellow. The antimony penta-sul- 
phide (Sb 2 S 5 ) is used for vulcanising rubber. The sulphides of anti- 
mony are used as a basis for the production of a number of pigments. 

TANTALUM, NIOBIUM, AND VANADIUM. 

These elements are only obtained in the metallic state with dif- 
ficulty. Neither the first two nor any of their compounds have been 
put to any useful application. Vanadium is widely distributed but 
occurs in small quantities. Some of the vanadic compounds are used in 
the preparation of pigments, of aniline black, and for dyeing leather black. 

TIN; Sn. 

Tin is a metal of great antiquity. It is mentioned in the 
Bible and was one of the common metals in the time of Moses. 
Numerous bronze implements containing- tin have been found 
in the ruins of Ninevah. It is probable but not certain that 
the Phoenicians obtained the tin ore from what are now Corn- 
wall and Devon, more than 1000 years B. C. Some of the 
early bronzes contained tin and agree closely in composition 
with statuary bronze of the present time. The Romans used 
the metal for tinning the interior of copper vessels just as is 
done to-day. 



225 

Occurrence and Preparation. Tin has not been found 
native. It occurs in combination as a sulphide and as an oxide. 
The latter Sn0 2 is the ore from which nearly all the metal is 
obtained. The islands of Banca, Malacca, and the British 
Isles produce the greater portion of the tin. 

Tin Reduction. For reduction the best quality of tin ore 
is crushed and washed to remove as much of the gangue as 
possible. The ore is then mixed with coal and heated, usually 
in a reverberatory furnace, the air being excluded to favor 
the reducing action of the carbon. If the ore is refractory 
some flux is added to form a slag. The metal thus obtained 
is fused and cast into blocks which are fused again and the 
tin refined thus giving several grades of quality. 

Properties of Tin. Pure tin is nearly the color of silver. 
It is soft and malleable at ordinary temperatures and emits a 
crackling sound when bent or twisted. It is the most fusible 
of the common metals (227° C. ) . It is intermediate in hardness 
between lead and zinc. Its specific gravity is 7.3. Its malle- 
ability increases up to 100° C. ; at this point its malleability 
is onl^exceeded by gold, silver, and copper. Heated near to 
its boiling point it becomes brittle. It has little tenacity. It 
is little affected by air and moisture at common temperatures, 
but if kept fused in contact with the air it oxidizes rapidly 
forming a white powder. It is readily soluble in hydrochloric 
acid with evolution of hydrogen and dilute nitric acid acts 
upon it with great energy converting it into a white powder. 

According - to Bloxam extreme cold converts tin into a modification 
known as grey tin. The specific gravity of grey tin is only o.7o and 
when fused it becomes ordinary tin. Spontaneous disintegration may 
occur from great reduction of temperature. 

Uses of Tin. Tinning. Owing to its permanence under 
ordinary influences and its resistance to vegetable acids, tin 
is largely used for coating other metals. The manufacture of 
tin-plate absorbs more tin than any other industry. Tin-plate 

15 



226 

(or the material of which ordinary articles consist, called tin) 
is made by coating* iron or very mild steel with tin. Steel 
which is now most generally used is first carefully annealed. 
The annealed steel or iron plates are first carefully cleaned so 
as to present a chemically clean surface. The cleaned plates 
are then dipped once or twice into melted tin. The tin coat- 
ing protects the iron or steel plate so long as the surface is 
unbroken, but when the iron is exposed the two metals form 
an electric pair and the iron is most readily attacked and eaten 
away. With a zinc coating under similar circumstances the 
zinc is attacked. 

Tin-plate is made in large quantities in Europe and the 
industry is now being introduced into this country. Tin is 
also used to coat the interior of lead or other pipes used by 
brewers, distillers, and others. 

In terne plate the coating is an alloy of tin and lead. 

Culinary utensils are frequently tinned inside. This process 
is simple and has been practiced for many centuries. The 
surface of the utensil to be tinned which may be copper, brass, 
or iron, is made chemically clean. Some tin melted in the 
vessel is then spread over the surface with tow. A skillful 
workman thus produces a thin uniform layer of tin, which 
greatly increases the wearing power of the vessel and almost 
imperceptibly adds to the weight. So slight is the increase 
of weight that the Ancients thought that there was none and 
Pliny expresses surprise at so remarkable a result. 

Alloys. Tin enters into the composition of a large number 
of alloys. It alloys with lead in all proportions and many 
solders and pewters are^composed of these metals, all of which 
melt at temperatures lower than does either constituent. In 
applying a solder the surfaces to be joined should be chemi- 
cally clean and borax or sal-ammoniac is generally applied to 
dissolve off any oxide. 

Gun metal and bronze are alloys of copper and tin. 



227 

Oxides and Salts of Tin. Besides the binoxide of tin (Sn0 2 ) there is 
a monoxide (SnO). Each of these oxides forms a series of salts, the 
first acting as an acid and the second as a basic oxide. There have 
been obtained several other oxides. The stannic oxide by hydration 
forms two important acids the stannic and meta-stannic. These acids 
form a large number of salts the most important of which is the 
sodium stannate, largely used as a mordant in dyeing and calico 
printing. 

Tin forms two classes of salts (stannic and stannous) correspond- 
ing to both hydracids and oxyacids. None of these salts are of great 
technical importance though some of them are used in dyeing and 
calico printing. Several tin salts of vegetable acids (oxalate, acetate, 
citrate, and tartrate) are similarly used. 

TITANIUM, ZIRCONIUM, THORIUM, GERMANIUM, AND CERIUM. 

These four metals are among the rare elements and have found 
no useful applications. Titanium is remarkable in that it combines 
directly with nitrogen when strongly heated in air. Titanic acid has 
been employed in the manufacture of artificial teeth. The oxide of 
thorium together with those of cerium and zirconium is used in the 
preparation of the mantle of the Wellsbach burners. The other com- 
pounds of these metals are not of technical importance and can not be 
described here. 

LEAD; Pb"; 207. 

Occurrence. It is doubtful whether lead has ever been 
found in the native state, but it occurs in a large number of 
natural compounds. Only a few of these compounds can be 
classed as ores of lead. The sulphide or galena, PbS, is the 
most abundant and principal ore of lead. The carbonate 
and sulphate are met with in certain localities in suffi- 
cient quantity to form important ores. The compounds of 
lead with oxygen, sulphur, and arsenic are also frequently 
sources of lead, especially in the working of such compounds 
for the silver contained. 

METALLTJKGY OF LEAD. 

Until about 1870 substantially all the lead in commerce 
was obtained from galena or galenite, PbS. This ore is still 
the source of nearly all the lead, but the metal itself is now 
obtained in enormous quantity as a bye-product in the reduc- 
tion of silver. In these cases in addition to the lead sul- 



228 

phide there are often present several other compounds of 
lead, mainly those above mentioned. Lead is obtained in 
silver and gold mining in such large quantities that the 
method of producing the enriched lead or "base bullion, " as 
it is called, might with equal propriety be described along 
with those metals. 

The method of obtaining the lead from the galena is 
simple in principle and execution when the ore is compara- 
tively pure, but with impure ore the processes increase in 
complexity and number. The processes may be conveniently 
separated into three: 1st. Hie method of self deduction; 2nd. 
The method of roasting, oxidation, and subsequent reduction 
by carbon; 3rd. Reduction by iron. 

First Process. The simplest method of reduction is 
carried out in a reverberatory furnace and is usually termed 
the air reduction or self-reduction method. In this method 
the galena is roasted at a moderate heat and partially con- 
verted into the oxide and sulphate. The temperature is then 
raised and the unchanged sulphide reacts upon the oxide 
and sulphate, freeing the lead. 2PbO-PbS = SO L -3Pb and 
PbS+PbS0 4 =2Pb+2S0 2 . A small quantity of lime is 
usually added with the ore for the purpose of forming a slag 
with the siliceous matter present. This method is applicable 
to the purer forms of galena. The other two methods to be 
mentioned are applicable to ores poorer in lead or associated 
with other minerals which make their reduction in reverber- 
atory furnaces impracticable. 

Second Process. The second method consists in convert- 
ing the galena into oxide and reducing the oxide with car- 
bonaceous matter. 

In this method the ore is first roasted until free or very nearly free 
from sulphnr. It is then mixed with fuel and flux (iron oxide and lime) 
and smelted in a blast farnace. The lead is reduced by the carbon- 
aceous matter and the impurities are removed as slag. The first heat- 
ing in the process is generally accomplished in a calciner (a kind of 
reverberatory furnace I . 



229 

The Third Process. In this process the raw ores are 

treated direct in a blast fnrnace and the reducing" agent is 

iron, PbS+Fe=Pb+FeS. In this method the ore is treated 

in a blast furnace and there is added to the charge, if iron 

oxide is not already present in the ore, metallic iron or more 

generally rich iron slags or iron ore. In the latter cases the 

iron ores are reduced by the carbonaceous matter of the fuel 

and the melted iron decomposes the galena, freeing the lead 

and forming iron sulphide as indicated above. 

The iron sulphide formed combines with some of the lead sulphide 
and other sulphides present in the ore and yields a matte which is 
lighter than the lead and easily separated from it. The matte is sub- 
jected to other treatment for saying the lead, copper, and silver when 
the latter are present. The slags of the first and second processes are 
often treated by the third method. Some lead ores are treated by two 
of the above processes. Galena has also been reduced by iron directly 
in a reverberatory furnace. 

American Western Method. The last two processes have 
been substantially combined in one in this country and it 
has been used extensively for the production of enormous 
quantities of argentiferous lead, notably at Leadville, Colo- 
rado, and Eureka, Nevada. The modified process consists 
in treating the raw ore direct in blast furnaces. If the 
gangue does not contain the necessary ingredients the ore is 
mixed with the proper material for flux and charged into the 
furnace with carbonaceous fuel. The charge of the furnace 
in general terms consists of the ore and gangue to which, 
depending upon their composition, is added one or more 
fluxes, as iron ore, siliceous matter, and limestone or dolo- 
mite. The result of the smelting operation gives three dis- 
tinct products, all of which are drawn from the same furnace 
in the liquid state. The lowest is the rich lead called "base- 
bullion," which is drawn off into pigs, preparatory to 
refining. The second is termed "speiss" and is principally 
composed of a combination of iron with arsenic and sulphur; 
antimony and other metals are often present in small quan- 



230 

tity. The third layer is the slag and consists essentially of 
the silicate of iron. 

The "speiss" is frequently divisible into two parts, the 
" speiss " proper and the matte ; the matte is mainly iron sul- 
phide, the " speiss " proper is iron combined with arsenic and 
antimony. The matte carries more silver than the "speiss" 
proper and is sometimes worked over. The "speiss" carries 
more gold than the matte and some silver, but no way of 
extracting the gold economically has been invented. This 
"speiss" has been produced in great quantities at the west- 
ern smelting works and contains a large amount of gold and 
silver. 

In the smelting of lead ores considerable quantities of 
lead fume are carried off with the smoke from the furnaces 
and many processes have been tried for the collection and 
saving of this lead. The method usually adopted is to cause 
the furnace gases to pass through a series of flues aggre- 
gating several miles in length. The lead fume settles very 
slowly even in quiescent air, which fact explains the great 
length of the flues. These flues are cleared out at intervals 
and much fume secured. The fume consists of lead sul- 
phate, lead oxide, and lead sulphide. 

DESILVEEIZING LEAD. 

When lead from any of the above sources contains 
enough silver to make its extraction profitable it is desilver- 
ized. The production of the lead at many of the western 
works is but the first step toward obtaining the accompany- 
ing silver and such lead is always desilverized. The silver 
can be extracted with profit when the lead contains one 
ounce of silver to the ton. 

The desilverizing process involves three distinct operations 
— "softening," concentration, and cupellation. The object 
of the first is to remove base metals which would interfere 
with the separation of the silver and lead; the second is to 
concentrate the silver in a smaller quantity of the lead; the 



231 

third is to complete the separation of the silver from the 
remaining' portion of the lead. 

The preliminary operation to the concentration is " soften- 
ing* " the lead, sometimes in our western states merely termed 
"calcining." The object of "softening" is to remove from 
the lead antimony, copper, or other oxidizable metals as 
fully as possible. This removal is accomplished by taking 
advantage of the difference of fusibility and difference of 
oxidizability. The "softening" is effected in a reverberatory 
furnace. The smelted lead is fused at a low temperature 
and the copper being the less fusible can be partially re- 
moved as a scum from the lead, which fuses first. The 
heated air plays upon the molten metal by which the more 
oxidizable bodies are converted into oxides which float upon 
the surface and are removed. This continually exposes fresh 
surfaces of the metal to the action of the air and facilitates 
the oxidation of the impurities. When the impurities are too 
abundant for this ordinary treatment, the melted metal is 
agitated by a jet of steam discharged into it which is more 
efficient in exposing the metal to the action of the air. In 
this operation some of the lead is of course oxidized and 
carried off with the other impurities, but these oxidized 
products are all worked over again to recover the metals 
contained. These products from the "softening" furnace are 
called "crasses," the term slag having very appropriately 
been limited to fusible silicate. 

Parke's Desilverizing Process. After " softening " the 
further concentration of the silver in the lead or the desilver- 
ization of the "base-bullion" in this country, is accomplished 
by Parke's desilverizing process. This process depends upon 
the fact that zinc alloys more readily with silver than with 
lead, and when zinc is melted with argentiferous load and 
the mixture allowed to cool, the portion which first solidifies 
is an alloy of silver, zinc, and lead containing nearly all the 



232 

silver and only a small amount of lead. The zinc employed 
amounts to about two per cent of the lead treated. 

From the rich alloy of zinc, lead, and silver, the zinc is 
separated by distillation and used again. The remaining" 
alloy of lead and silver is subjected to cupellation which 
separates the silver from the lead. The cupellation will be 
described after we have explained the principles of another 
important process for concentration. 

Pattinson's Desilverizing Process. This process depends 
upon the fact that an alloy of lead and silver is more fusible 
than the lead itself. In Pattinson's process the argentife- 
rous lead is melted and allowed to cool slowly while being 
constantly stirred. Near the melting temperature of the lead 
this metal crystallizes out carrying only very minute quanti- 
ties of silver — these crystals are continually removed and the 
lead left behind is very rich in silver. 

A modification of the Pattinson process consists in agita- 
tion of the molten metal by a jet of high pressure steam — 
this facilitates the crystallization of the lead and removes 
more fully copper and antimony; it also saves time and labor. 
In this method the enriched alloy is drawn off in the liquid 
state from the lead. This modified process is known as that 
of Eozan. It was long employed at the Eichmond mines at 
Eureka, Nevada, and is not used elsewhere in this country. 

Cupellation. The rich lead obtained by either of the pro- 
cesses just described is then subjected to cupellation or refin- 
ing. This operation depends upon the fact that the melted 
lead readily oxidizes in air while silver does not. The fine 
lead is melted in a cupel on the hearth of a reverberatory 
furnace. The cupels are about four or five feet long and two 
or three feet wide and six or seven inches deep. They are 
made of bone ash and pearl ash. Over the melted surface 
of the lead a blast of air is made to play. The lead is rap- 
idly oxidized and the blast drives the oxide to the mouth of 



233 

the refinery where it flows out in the liquid state into pots 
and is removed. As the oxidation proceeds more lead is 
added and the operation is not generally completed in a 
single cupel. When the silver amounts to about one-tenth of 
the contents the concentrate is drawn off and the oxidation 
completed in a second cupel. The oxide of lead which is 
removed carries some silver and is always reduced again. 
The bottoms of the cupels become saturated with lead oxide 
and are broken up and smelted in the blast furnace. 

Properties of Lead. Lead is a bluish grey metal. It is 
so soft as to leave a streak when rubbed on paper. It is 
malleable and ductile but has little tenacity. Its hardness is 
increased by zinc, antimony, and copper. Its specific gravity 
varies with the conditions under which it is obtained but is 
about 11.3. Its fusing point is 235° C. It is readily oxidized 
in the presence of moist air and then in the presence of acid 
vapors forms salts. The basic carbonate of lead thus often 
results from the action of the carbon dioxide of the air. In 
a finely divided state lead is pyrophoric. 

The action of water upon lead is influenced by the salts 
dissolved in the water. Nitrites and nitrates increase the 
action of water upon lead and the sulphates and carbonates 
decrease this action. The fact that lead is a cumulative 
poison and that water long in contact with it is liable to con- 
tain some lead, make great care necessary in using waters 
that have been in contact with lead. Water that has been 
standing long in lead pipes or conveyed for long distances in 
such pipes should not be habitually used for drinking. 

Dilute nitric acid acts readily upon lead but it resists the 
action of all the other common mineral acids when at the 
common temperature — even hydrofluoric acid does not attack 
it. Hot concentrated hydrochloric and sulphuric acids act 
upon it. 

Uses of Lead. Lead is largely used in the form of sheets, 
water channels, pipes and in construction work. Its resist- 



234 

ance to the action of acids make*it very useful in sulphuric 
acid works and in many appliances of the chemical labora- 
tory. It finds many uses in the preparation of alloys, type 
metal, pewter, solder, &c. 

It is the metal from which shot are made and for this pur- 
pose the molten metal is caused to flow through cullenders 
of proper size and to fall for some distance through the air 
into vessels holding water. A small amount of arsenic (two 
per cent) is always alloyed with the lead in this operation. 
The arsenic makes the lead more fluid, hardens it when 
cool, and increases its tendency to take the spherical form in 
passing through the air. The size of the holes in the collen- 
der, which must be smooth and round, the temperature of 
the melted lead, and the distance through which it falls 
determine the size of the shot. The length of the tower 
varies from thirty feet for small to fifty feet for large shot. 

Lead pipes are usually made by forcing the melted metal 
through the annular space between a die and a concentric 
spindle or mandril, the die fixing the exterior diameter of 
the pipe and the mandril the interior. The largest amount 
of lead is consumed in the manufacture of white lead. 

Lead Oxides. There are five oxides of lead known, the 
most important of which are the monoxide and red lead (PbO 
andPb 3 4 ). 

Lead Monoxide; PbO. This body occasionally occurs 
native. There are two varieties of the artificial product mas- 
sicot and litharge. Massicot is produced when melted lead 
is heated at a comnaoB-moderate temperature in the air and 
it is a yellow powder. "When the oxidation takes place at a 
temperature sufficiently high to fuse the oxide formed, it 
gives litharge, which is reddish brown in color. Litharge 
readily combines with silica at high temperature and forms 
lead silicate. It is largely used in the manufacture of flint 
glass and in glazing earthen ware ; it is also used for the pro- 
duction of lead acetate and other lead salts. 



235 

Bed Lead; Minium; Phd. Red lead is made by heating 
massicot in air at a temperature not high enough to fuse it. 
It is largely used in the manufacture of flint glass, as a 
cement in steam joints, as an oxidizing agent in the manu- 
facture of matches, and as a pigment. 

White Lead; Basic Lead Carbonate. The commercial white 
lead is essentially a basic carbonate, which results from the com- 
bination of the normal carbonate with one or more molecules of 
lead hydrate, 2PbC0 3 , Pb(OH) 2 . Many methods have been 
invented and tried for the manufacture of this important 
compound. All of these which have been commercially 
successful depend upon the same principle, the formation of 
a basic salt of lead and the decomposition of this salt by 
carbon dioxide. The oldest method (the Dutch method) and 
that which still gives the best white lead for paints depends 
upon the formation of a basic acetate of lead and the conver- 
sion of this into white lead by carbon dioxide. In this 
method thin sheets of metallic lead are exposed to the com- 
bined action of the vapor of acetic acid and carbon dioxide. 
The lead is gradually converted into white lead, which has 
to be separated from the metallic lead, ground, and washed. 
The chemical actions which produce the result are, first, the 
production of a normal lead acetate which combines with the 
lead hydrate to form basic lead acetate. Then the carbon 
dioxide decomposes the basic acetate forming basic car- 
bonate and reproducing the normal acetate. This action is 
then repeated so that the acetic acid acts as a carrier 
between the lead and the carbon dioxide. A small amount 
of the acetic acid will convert a large amount of lead into the 
carbonate. The above method is also used in England. 

White lead by this method has retained its superiority 
over all others as a pigment. This superiority consists in 
greater covering power, durability, and opacity. These 
properties are believed to be due to the fact that the Dutch 



236 

pigment in its ultimate constitution is less crystalline and 
more nearly amorphous than that from any other source. 

Various efforts have been made to hasten the process for the pro- 
duction of white lead among which are the German and French 
methods. In the former the actions described are aided by artificial 
heat the reagents being enclosed in stoves. The French method 
(Clichy) involves the separate preparation of lead oxide and the action 
of acetic acid upon it, the result being treated with carbon dioxide. 
This method slightly modified is largely used in this country. Another 
process (Milner's) consists in the production of a basic chloride of lead 
by the action of litharge, common salt, and water upon each other and 
the subsequent precipitation of the chloride with carbon dioxide. The 
above processes are all that have succeeded commercially and while the 
newer processes are cheaper than the Dutch the product is not as 
valuable as a pigment. 

A new American method has just been announced by which the 
pigment is prepared by electrolysis. Sodium nitrate is decomposed by 
the electric current between lead and copper electrodes. Lead nitrate 
and sodium hydroxide are thus formed and dissolved at the two 
electrodes. The solutions are drawn off and mixed in the proper 
proportions when sodium nitrate is reproduced and lead hydrate 
precipitated as an amorphous powder. This nitrate may be again 
electrolysed. A solution of sodium carbonate is added to the lead 
hydrate by which sodium hydroxide and basic lead carbonate are 
formed. The hydroxide of sodium can again be converted into the 
carbonate by carbon dioxide and used again. The sodium nitrate and 
carbonate being repeatedly used are only consumed in small quantities. 
The advantages of this process are that no free acids are used, that the 
operation is complete in a day, and that the process is non-poisoning — 
the pigment being produced in the form of powder and no grinding 
being necessary. It is claimed that the product is more amorphous 
than the Dutch pigment and consequently superior to it. 

Properties and Uses of White Lead. The pigment is a 
heavy white powder. It is poisonous and the separation 
and grinding- of the product in the English-Dutch method 
often leads to lead poisoning among the operatives. The 
difficulty of avoiding these effects constitutes a grave objec- 
tion to the process. 

The principal use of white lead is for painting. It is 
thought that when white lead is mixed with oil it saponifies 
some of the oil and that to this fact is partly due its superi- 



237 

ority as a pigment. Lead paints are discolored by hydro- 
gen sulphide from the formation of lead sulphide. 
Painting" which has been blackened thus may often be 
restored by exposure to light and air by which the sulphide 
is oxidized to the sulphate. White lead is sometimes adulte- 
rated with barium sulphate and certain pigments are made 
by mixing the two in certain proportions. It has been pro- 
posed to use lead sulphate as a substitute for white lead but 
none of these products give as good results as the pure 
pigment. 

Other Compounds of Lead. In addition to the compounds of lead 
already referred to there is a number of others, none of which are of 
any commercial importance nor of special use in the laboratory. Some 
of the oxychlorides are used to a limited extent as pigments — Pattin- 
son's oxychloride gives a white pigment and Paris yellow and Turner's 
yellow belong to this class of bodies. 

COPPER; Cu; 63.2. 

Occurrence. Copper occurs abundantly in the native 
state and as a constituent in many natural compounds. 
Among these compounds the principal ores of copper are the 
oxides, carbonates, and various sulphuretted forms. These 
last constitute the most abundant ores of copper and the 
most important of them is the copper pyrites, a double 
sulphide of copper and iron (Cu 2 S, Fe 2 S 3 ) though there are 
several other sulphides of copper. 

These ores of copper in addition to the gangue are very 
frequently associated with the sulphides and arsenides of 
other metals as iron, antimony, lead, zinc, and silver; gold is 
also often present. 

Copper Reduction. Copper is obtained from its ores by 
two processes usually termed the tvet and dry, the latter 
involving fusion and the former not. The method involving 
fusion is the more important industrially. The object of the 
reduction is of course in all cases to separate the copper from 
the impurities present. 

In the United States the great bulk of the copper is 



238 

obtained from three localities, the region of Lake Superior, 
from Montana, and from Arizona. In the Lake Superior 
region the copper is mainly in the native form, in Montana 
the sulphuretted compounds exist, and in Arizona the 
oxidized forms abound together with the sulphides. The 
dry method or the method of fusion is employed in all these 
localities. 

Dry Reduction. 1, Concentration of Native Copper; Lake 
Superior. Although there have been found immense masses 
of native copper in these mines varying from forty to four 
hundred tons, these large masses have not been the principal 
sources of the metal. The bulk of the copper of these mines 
is distributed in fine grains through the gangue stone, which 
is either amygdaloid or conglomerate rock. The rock is 
crushed by steam stamps in the mill and the metal is 
separated from the gangue by washing. The crushed «retal <^ 
in its descent over a series of cradles which are continually 
"jigged" or given a jerky motion, is subjected to the action 
of running water. By this means the metal which is heavier 
collects below the sand, the larger grains nearer the stamps, 
the moveable earthy matter being carried along by the water. 
At the lower end of the incline the finer sediment is sub- 
jected to special treatment on sluice-tables or "buddlers" to 
collect the very finely divided copper. 

The gangue remaining with the copper is separated by 
fusion with a little flux in a reverberatory furnace and 
copper of great purity obtained. The ores from which the 
copper is obtained vary in richness from .6 to 3 per cent of 
metal. The method of obtaining the copper from the ore at 
Lake Superior is so simple that it is usually termed mechan- 
ical concentration, but since the product is fused and refined 
it is here included under dry reduction. 

Dry Reduction. 2, Reduction of Oxidized Copper Ores. 

In the Arizona mines a large part of the ores worked a& the 
present time have been oxidized forms. These are reduced 



239 

in blast furnaces, coke being" generally the fuel employed. 
The purity of the oxidized ores (oxides and carbonates) fre- 
quently permits the production of a high grade of copper by 
the single operation of smelting in the blast furnace with 
carbonaceous matter as reducing agent. The Arizona cop- 
per ranks next to the Lake Superior in purity. In these 
mines the proportion of the oxidized ores decreases and of 
the sulphuretted ores increases as the depth increases. The 
reduction of the sulphides depends upon the principles to be 
described. 

Dry Reduction. 3, Reduction of Copper Sulphides. The 

sulphuretted ores of copper are those most largely employed 
throughout the world for obtaining the metal. These ores 
are extensively worked in the Western mines in this country. 
The sulphuretted ores are becoming more and more import- 
ant at the Arizona mines and considerable copper now comes 
from the copper bearing silver and lead ores of Colorado. 

In the reduction of the sulphides use is made of the prin- 
ciple that copper sulphide is less easily reduced than the 
other metallic sulphides present in the ore, of these iron is 
the most important. 

The older process of reduction consists of a series of 
roastings (heating in air) and fusions of the ore, the number 
of operations varying with the nature and quality of the 
ore. The object of the roasting is to expel arsenic, some 
of the sulphur and antimony, and to oxidize the iron. 
After the first roasting the ore is fused with the proper 
flux to form a slag with the gangue and iron oxide. In 
this operation the gangue and some of the iron are removed 
and coarse metal or a "matte" is obtained. The "matte" 
is essentially a double sulphide of copper and iron with 
greatly reduced quantities of antimony and arsenic. This 
"matte" is then broken up and the operation of roasting 
and fusion is again repeated by which "white" metal 
is obtained; this is copper sulphide nearly free from 



240 

iron and other base metals. The "white" metal has to be 
again fnsed in an oxidizing atmosphere by which self -reduc- 
tion takes place, Cu 2 S+2CuO=Cu4-f-S0 2 , and "blister" cop- 
per is obtained; or the oxidizing action may be continued 
until all the sulphur is expelled and the copper oxide formed 
reduced by carbonaceous matter. The "blister" copper has 
then to be refined to remove any remaining sulphur and the 
small quantities of the baser metals still left. During all the 
operations sulphur, arsenic, and antimony are gradually 
eliminated. The roasting of the ores and "matte" may be 
accomplished in heaps, or stalls (which are rectangular open 
brick enclosures) reverberatory furnaces, or roasting cylin- 
ders. The fusion of the roasted products is accomplished in 
reverberatory furnaces or shaft furnaces. 

It will be observed that the above method consists of a series of 
roastings in which the oxidizable impurities are oxidized together with 
some of the copper. These are followed by smelting operations by 
which the copper is deoxidized by some of the remaining sulphur and 
the iron removed as a slag. It would be impracticable to here describe 
in detail all the steps in the smelting of sulphuretted ores. The charges 
of one operation are often treated with fresh ore or with the products 
of another operation, the object in all cases being the removal of the 
base impurities present with the least possible expenditure of fuel and 
loss of copper. The stability of the copper sulphide and the easy reduc- 
tion of the copper oxide as compared to the similar compounds of 
other elements present are the basis of the method pursued. The ope- 
rations are sometimes more and sometimes less numerous than above 
indicated depending upon the nature of the ores and the necessity for 
economy in working. 

Bessemerizing Copper " Matte." In this country in the 
past ten years the practice of Bessemerizing the copper 
"matte " has become very general. In this operation the 
principle of the Bessemer steel converter is applied to the 
purification of the copper "matte" (sulphide of iron and 
copper). The "matte" in the liquid state is run into the 
converter and the blast of air turned on. The liquid condi- 
tion of the contents is kept up by the heat resulting from the 
combustion of the iron and sulphur by the oxygen of the air. 



241 

The iron oxide forms a slag" with the siliceous lining' of the 
converter and is thus removed; the sulphur is oxidized and 
passes off as sulphur dioxide. In this country it is usual to 
pass from the "matte " to "blister" copper by a single blow- 
ing", the blow being" stopped once or twice to draw or skim off 
the slag". In accomplishing" this result the "matte" must 
contain about 50 per cent of copper. The charge for the con- 
verter may be obtained either by remelting in a cupola 
furnace the "matte" obtained in the first operation of 
smelting or by running the "matte" directly from the reduc- 
ing furnaces to the converter. In the smelter at Great Falls, 
Montana, the latter plan is in operation. There the convert- 
ers are directly in front of the furnaces and the general 
arrangements are similar to those of a Bessemer steel plant. 

Under the conditions of our western copper mines the 
savings of fuel, labor, &c, by the Bessemer modification 
has caused a very great application of it. 

Pyritic Smelting Without Fuel. An attempt which has met with 
some success, has been made in this country to extend the principle of 
the converter to the direct reduction of the native ores in blastfurnaces 
without the use of any carbonaceous fuel. In this process it is aimed 
to oxidize the impurities of the ore and to develop the necessary heat 
by this oxidation to remove the impurities themselves and obtain the 
metal by a single operation in the blast furnaces. The blast furnace is 
thus made to play the part of a huge Bessemer converter. 

The pyritic smelting by the heat resulting almost entirely from the 
oxidation of the ores employed has been successfully accomplished but 
it has not been sufficiently developed to determine its probable import- 
ance. The term pyritic smelting has been in use a long time and the 
process just mentioned under this heading differs from previous ones 
employed, in that the pyritic ores are required to supply the fuel for 
their own reduction, to act as a. menstrum for collecting the precious 
metal and as a factor in slag production. In the older pyritic reduction 
the sulphuretted materialwas merelyused as a collector of the precious 
metals and not for the second and third purposes. 

Copper Reduction by the Wet Method. This method de- 
pends upon the conversion of the copper in the ores into a 
soluble form and the precipitation of the copper from solu- 
tion. The niothod is in general applied to the ores that are 



242 

very refractory or are poor in copper. The copper salts 
commonly produced are the chlorides and sulphates. The 
copper oxides or sulphides may be converted into chlorides 
by roasting with common salt or treating the ore with a 
solution of ferric chloride or hydrochloric acid. The sulphide 
ores may be converted into sulphate by carefully roasting or 
by exposure to air and moisture; such change often occurs 
in the natural ore beds. The oxidized ores may be converted 
into sulphates by the direct action of sulphuric acid or by 
roasting with iron sulphate. 

Metallic iron added to the solution of the sulphate or 
chloride precipitates the copper [jpi metallic condition. The 
precipitated copper has to be m l kd and refined. 

Electrolytic Refining of Copper and the Extraction of 
Silver and Gold. In the smelting of copper by fusion as 
above described any gold or silver that is present in the ore 
is retained by the copper. In much of the copper produced 
it is commercially profitable to extract the precious metals. 
The native copper from Lake Superior is not generally 
refined for silver or gold, but a large portion of that from 
Montana, Arizona, and Colorado contains these metals in 
paying quantities. The Bessemerized or other metallic cop- 
per from these sources is now largely refined by electrolysis. 

For this purpose the copper is cast into plates about 
three inches thick weighing 275 or 300 pounds. These plates 
are made the anodes in decomposing cells, the kathodes 
being thin sheets of copper themselves formed especially for 
this purpose «§, electrolysis. The electrolyte employed is the 
sulphate of copper in solution. Under the influence of a power- 
ful electric current the anode plates are rapidly transferred 
to the kathodes while the gold and silver fall as "slimes" in 
the vats. The kathode plate being of electrolytic copper the 
entire mass of metal at that plate is deposited copper. This 
process gives copper of a high degree of purity but it is not 
equal to the native copper. 



243 

The deposited copper has to be subjected to fusion to 
destroy its crystalline texture before it is fit for industrial 
purposes. The "slimes" are subjected to the action of dilute 
sulphuric acid by which the copper is dissolved out — the 
residue is fused and the gold and silver separated either by 
electrolysis or by dissolving the silver out with sulphuric 
acid. The silver sulphate is reduced by metallic copper or 
iron. 

Separation of Silver from Copper "Matte"; Ziervogel Method. 

This method depends upon the fact that by carefully roasting the ar- 
gentiferous copper "matte" (sulphides of silver, gold, and iron) the 
silver maybe left as a sulphate while the iron and copper are converted 
into oxides, their sulphides being first formed and then decomposed. 
The sulphide of silver can then be dissolved out from the two oxides. 
The silver is precipitated from the solution by metallic copper. 

2. Ligation Process. The crude copper before refining is some- 
times subjected to the lignation process for the separation of the silver. 
In this process the argentiferous copper is fused with about three times 
its weight of lead. The lead alloyed with the silver is much more 
fusible than the copper and by careful cooling this rich alloy may be 
nearly entirely separated from the copper. The silver is then separated 
from the lead by cupellation. 

Properties of Copper. Copper is a valuable metal in the 
arts. Its specific gravity is about 8.9, a little lower than 
iron. It is very malleable, ductile, and tenaceous. Among 
the common metals it is next to gold and silver in mallea- 
bility, and next to iron in tenacity. It fuses at a lower tem- 
perature than iron. It is one of the best conductors of heat 
and electricity. Its ductility, malleability, and conductivity 
are greatly diminished by even minute quantities of impuri- 
ties. Copper is only slowly affected by exposure to dry air 
at common temperature. In the presence of the moisture 
and carbon dioxide of the air, it becomes covered with a 
green carbonate commonly but improperly called verdigris. 

Dilute hydrochloric and sulphuric acids do not act upon 
copper if air be excluded. Hot sulphuric acid acts readily 
upon it. Nitric acid in any form acts upon it, though the 



244 

presence of nitrous acid is said to be necessary to begin the 
action. 

Uses of Copper. Copper is used very extensively, the 
most important Use being 1 in the construction of electrical 
machinery and apparatus, for the manufacture of boilers, 
chemical stills and apparatus, kitchen utensils, cartridge 
cases and as sheathing for vessels. In sea water the 
copper is corroded, due to the formation of the oxy chloride. 
This roughens the surface and gives points of attach- 
ment for barnacles and other salt water forms, which often 
greatly impede the sailing power of vessels, many tons 
of these animals having been removed from a single vessel. 
Numerous attempts have been made to protect this sheath- 
ing from corrosion. 

Cooking utensils of copper should always be kept perfectly 
bright to avoid the formation of poisonous salts by the acids 
of food. Even then the joint action of the air and the vege- 
table and other acids often present may contaminate the 
food. This fact justifies the custom of coating the interior 
of such vessels with tin. Copper is also used in making 
electrotypes and as a constituent of many useful alloys. 
Bronze is composed of copper and tin and brass of copper 
and zinc. 

Compounds of Copper. The Oxides. Among the com- 
pounds of copper employed otherwise than as ores may be 
mentioned the black and red oxides (CuO and Cu 2 0). The 
first is employed as a source of oxygen in organic analysis; 
the second is used in glass making, to impart a red color. 

Copper Sulphate. Copper sulphate may be prepared by 
dissolving copper in sulphuric acid or by the oxidation of 
copper pyrites. It is very largely employed in solution in 
forming electrotypes and in galvanic batteries. It is also 
largely employed in dyeing, in calico printing, and in the 
manufacture of pigments. 



245 

Carbonates of Copper. The native carbonates of copper 
when found in massive forms yield the minerals known 
as aznrite and malachite used in ornamental work. They 
are also used as pigments. 

Some of the other compounds of copper find limited application. 
The hydrated oxide dissolved in ammonia known as "Schweitzer's re- 
agent" yields a solution which dissolves cellulose. The eupric chloride 
finds some application in calico printing and in the manufacture of 
colors. 

SILVER; Ag; 108. 

Occurrence. Silver is a pretty widely diffused metal, 
though it occurs only in small quantities. It is found in the 
metallic state; its principal ores are the sulphide, the sul- 
phide in common with the sulphides of arsenic and antimony, 
the chloride, the iodide, and the bromide. All these are very 
generally associated with the sulphides of iron, lead, and 
copper. The sulphide is the ore yielding the most silver. 

Reduction of Silver From Its Ores. Silver being one of 
the precious metals and its ores being very varied and gen- 
erally associated with a large per cent of other material its 
metallurgy is very varied. The processes for obtaining the 
metal may be classed under three heads: 1st, Smelting; 
2nd, Amalgamation; 3rd, Leaching. 

Smelting for Silver. This process is applicable to the 
ores of silver which accompany the ores of lead and copper, 
these last named compounds being present in sufficient quan- 
tity to render their extraction possible and profitable by 
smelting. The success of the process depends upon the fact 
that in the operation of smelting and separating the lead and 
copper from the baser matter of the ore, the silver remains 
with the lead or copper. It may be said that when the silver 
ores are smelted with the ores of lead and copper that the 
silver ore is reduced with the ores of these metals and the 
silver dissolved and carried down by the lead or copper. 
The smelting of silver ores associated with lead and copper 



246 

ores is conducted on a large scale in this country. The man- 
ner of reducing the lead and copper ores has been described 
under those metals and the methods of refining these metals 
for obtaining the silver are also there described. These pro- 
cesses therefore include silver smelting. From the lead and 
copper ores of Colorado and from the copper ores of Arizona 
and Montana there is a large yield of silver. 

Amalgamation Process. This process depends upon the 
fact that mercury will reduce certain compounds of silver 
and that it dissolves or amalgamates metallic silver. The 
method is applied to a great variety of ores which, from their 
mineral associates or lack of fuel can not be economically 
smelted. The process is an old one and many slight varia- 
tions in the details of the process exist. The method most 
generally adopted in this country is known as the Washoe or 
"pan" process; it has been and is still largely employed in 
the West. 

If the silver exists in the ores in such form that they are 
readily amalgamated the process is largely one of mechan- 
ical detail. Such ores are in this country termed "free mill- 
ing," and the steps in the process are as follows: The ore is 
first crushed in a mortar by stamps. The stamping involves 
the principle of the pestle and mortar ; there are usually four 
or more stamps in operation in each mortar. 

In California a single mortar with its stamps is called a 
"battery." In the sides of the mortar are placed screens 
with the proper number of meshes and when the ore is suffi- 
ciently crushed it is carried through these screens by a 
stream of water flowing through the mortars. The mud 
from the mortars is charged into iron pans and ground to a 
fine pulp and amalgamated with mercury. The charges 
from the amalgamating pans are passed into tanks in which 
the mercury and amalgam are separated from earthy 
matters. The free mercury is then separated from the amal- 
gam by straining and the latter subjected to distillation, the 



247 

mercury passing off and the silver being left behind. The 
mercury is of course collected for future use. The direct 
process is especially applicable to ores rich in native silver, 
silver chloride, and not an excess of silver sulphide. 

Sometimes the ores rich in the sulphide are subjected to 
preliminary treatment before amalgamation. They are 
roasted with common salt by which they are converted into 
the chloride. The amalgamation then takes place directly, 
the mercury reduces the silver chloride and, the reduced sil- 
ver combines with another portion of the mercury — 
the amalgamation is frequently accomplished in barrels. 
AgCl+2Hg=HgCl+AgHg. This method was employed with 
certain ores of the Comstock Lode rich in silver sulphide 
and was formerly employed at other places but it is not 
now much used in this country. 

The ores from the great Comstock Lode of Nevada were mainly 
reduced by the pan process. The mechanical appliances in such Avorks are 
generally very extensive and consist of (1) the crusher, (2) the stamps, 
(3) pans for grinding: and amalgamating, (4) settlers for removing the 
settlings and amalgams from the pulp, (5) the agitators which are sup- 
plementary to the latter, (6) appliances for saving "slimes" and 
"tailings," (7) retorts for sublimation. The crusher breaks the ore 
when necessary into lumps. The stamps are heavy iron pestles lifted 
and dropped by machinery in iron mortars where the lump ore is 
crushed. A stream of water flows through the mortar and carries 
with it the pulverized ore. This water flows into tanks where it 
deposits the bulk of the earthy matter. The water flowing from the 
tanks always carries certain very fine material which is subsequently 
collected under the name of " slimes." From the tanks the crushed ore- 
is conveyed to pans for grinding and amalgamation. These pans are 
generally iron tubs about three feet deep and from four to six feet in 
diameter. They are arranged to grind the sand very fine and to thor- 
oughly mix it with the mercury, the grinding taking place mainly 
before the addition of the mercury. The settlers are tubs of iron or of 
wood with iron bottoms. In the settlers the pulp is diluted with water 
and the whole agitated to separate the mercury and the amalgam. The 
separation is still further accomplished in the agitators. The amalgam 
and mercury thus obtained are thoroughly washed, strained through 
canvas to separate them, and the amalgam distilled. Theearthy matter 
from the settlers and agitators is called "tailings," both the "slimes*' 
and "tailings" contain some silver and are sometimes subjected (the 



248 

former always) to a second treatment. The aboA T e process gives the 
principal steps in the production of "free-milling" ores; in all such oper- 
ations in the West there is universal practice of adding certain chemi- 
cals to the charge in the pan. The so-called chemicals are sodium 
chloride and copper sulphate. The action of these chemicals is uncer- 
tain and by some good authorities their beneficial effect is doubted. It 
is thought most likely to be represented by the following reactions. 
2NaCl+0uSO 4 — Na 2 SO 4 +Cu01 2 ; 2CuCl 2 +Ag,S=2AgCl+2CuCl+S; 2CuCl+ 
Ag 2 S=2AgCl+Cu 2 S ; AgCl+2Hg=AgHg+HgCl. 

When the ore is stamped without preliminary treatment it 
is known as wet stamping. In wet stamping" the crushed ore 
is carried from the mortars through the screen by running 
water. When the ores are subjected to a preliminary drying 
or roasting with or without salt the process then involves dry 
stamping. In the dry stamping the crushed ore is driven 
through the screens by the impulse communicated by the 
stamps. In this case the front of the screen is enclosed by 
dust-tight boxes and special arrangements are made for 
removing the crushed ore from the boxes. Dry stamping is 
now principally used with the leaching process yet to be 
described. The drying and roasting necessitate of course 
different additional appliances at works to accomplish these 
results. The roasting of ores in our western country is 
almost entirely effected in some form of mechanical furnace. 

There are two types of these furnaces, the horizontal rotating and 
the vertical shaft. The Bruckner rocl i ooing cylinder may be taken as an 
illustration of the first. This cylinder is from twelve to sixteen feet 
long and five to seven feet in diameter, composed of iron shells; the 
whole is lined with brick. Passing through the cylinder from side to 
side is a number of pipes which form a sort of diaphragm. One end 
of the cylinder fits into a fire-box and the other into a chimney. The 
flame from the fire-box is made to play through the' cylinder. The 
cylinder revolves about its longer axis and the motion, in connection 
with the diaphragm, keeps the ore properly exposed to the action of 
the fire. 

The vertical furnace is a small shaft furnace surmounted by a 
charging apparatus which is operated mechanically and which feeds 
the ore to the furnace with the greatest regularity and exactly as 
demanded. The Sledefelt is the commonly used furnace of this type. 

Leaching Process. This process is applicable to ores of 
silver which either from their nature or motives of economy 



249 

can not be treated by smelting* or amalgamation. It is 
generally practiced upon poor or what are called "rebellious" 
ores from the difficulty of working them by other methods. 
It depends upon the fact that certain silver compounds can 
by difference of solubility, be separated from accompanying 
minerals and then the silver obtained by simple treatment. 
The method usually followed in this country (that of Von 
Patera) is to roast the silver ore, generally silver sulphide, 
with common salt by which the silver is converted into the 
chloride. The roasted ore is then leached with water to 
dissolve out such substances as are soluble in that liquid. It 
is then leached with some solvent generally sodium or 
calcium hyposulphite which dissolves the chloride. The 
silver may then be precipitated as silver sulphide by adding 
calcium or sodium sulphide. The silver sulphide is then 
roasted and cupelled. 

In this process the ore is first dried, crushed by dry 
stamping or rollers, and then roasted with sodium chloride. 

The roasting' is done in the Brhckner cylinder already described. 
Mr. Russell has modified the process by leaching a second time with a 
mixture of sodium and copper hyposulphite (made by adding copper 
sulphite to sodium sulphite). The second leaching dissolves out native 
silver and the sulphide of silver. To this solution he adds a solution 
of sodium carbonate which precipitates the lead salts as lead carbon- 
ate ; the lead salts may be thus separated. The subsequent operations 
are as described in the Von Patera process. The Russell process is 
applicable to ores and "tailings" containing the native metal, the 
sulphide, and greater quantities of the baser metals than can be satis- 
factorily worked by the Von Patera process. 

In the old Freiburg method the roasted silver ore is agitated witli 
scrap iron and mercury in barrels. The iron reduces the chloride of 
silver and the metal then combines with the mercury. The amalgam 
is heated in a retort to separate the silver. The Ziervogel process of 
separating silver from copper "matte" (described under copper) in- 
volves the leaching of the silver sulphate from a "matte" prepared In- 
fusion. It therefore is not here included under the leaching process. 
though it is sometimes so classed. 

Properties of Silver. Silver has been known from re- 
mote antiquity. Its general appearance is familiar to every- 



250 

one. It is slightly harder than gold and softer than copper. 
Its specific gravity varies slightly with mode of preparation 
but is about 10.5. Next to gold it is the most malleable 
metal. It is very ductile, one grain may be drawn into a 
wire 400 feet long. It contracts in solidifying from the 
molten state. It is the best conductor of heat and electricity. 
It fuses at about 950° C. and can be distilled without dif- 
ficulty. Molten silver absorbs over twenty times its volume 
of oxygen which is given off with the exception of seven- 
tenths of one volume on cooling. 

It is not oxidized in the air, dry or moist, at any temper- 
ature, though it is oxidized by ozone. It is tarnished by 
hydrogen sulphide in the presence of air with the production 
of silver sulphide. Pure hydrogen sulphide does not attack 
silver. This tarnish is readily removed by potassium 
cyanide. It is readily acted upon by nitric acid with the 
production of silver nitrate. Hot concentrated sulphuric 
acid acts upon it with the formation of the sulphate. Boil- 
ing hydrochloric acid acts upon it. It resists the action of 
fused alkaline hydroxides better than platinum and is 
consequently more frequently used in the laboratory for 
crucibles, &c. 

Uses of Silver. The principal uses of silver are for coin, 
jewelry, photography, and for silvering other metals and 
alloys. The coin of the United States is composed of nine- 
tenths silver and one-tenth copper; for all other useful pur- 
poses it is similarly hardened. The plating of articles may 
be accomplished by electrolysis or silver leaf may be charged 
upon the properly prepared plate by burnishing. Silvering 
may also be accomplished by treating with an amalgam of 
silver, then heating to separate the mercury. The chloride 
of silver with certain reducing salts is likewise used to yield 
a film of silver. 

Frosted silver is prepared from standard silver by heat- 
ing to oxidize the copper and then dissolving out the oxide 



25 L 

by dilute sulphuric acid, this gives a surface of nearly pure 
silver and with a blanched, frosted appearance. 

The so-called oxidized silver is produced by immersing 
silver in a solution made by boiling sulphur in a solution of 
caustic potash. It is really the sulphide of silver. 

Pure silver may be obtained from the standard silver by 
dissolving the piece in nitric acid and precipitating the silver 
from the solution in the form of the chloride by the addition 
of a soluble chloride. The silver chloride may then be 
washed until all the copper salt is removed and heated with 
sodium carbonate, 2AgCl+Na a C0 8 =Ag 2 +2NaCl+0+C0 2 . 

Compounds of Silver; AgN0 3 . In addition to the ores of 
silver already mentioned there is a large number of com- 
pounds, the most important of which is the nitrate. The 
nitrate is prepared by dissolving silver in nitric acid, evapo- 
rating to crystallization and then fusing to expel free acid. 
It is used as a cautery in surgery and for this purpose it is 
usually cast into small cylindrical sticks. Its caustic prop- 
erties depend upon the facility with which it gives up its 
oxygen. It readily yields its oxygen to organic matter with 
the deposition of black metallic silver. There is nearly 
always sufficient organic matter in the air to cause the 
nitrate to blacken after exposure for a short time. This 
property accounts for the use of the nitrate for marking ink 
and as a constituent of certain hair dyes. The nitrate is the 
essential constituent of common indelible ink and the per- 
manent marking is due to the deposit of the finely divided 
silver in the fibre of the cloth. The nitrate is very largely 
used in the preparation of photographic plates. Stains upon 
the skin from the nitrate may be removed by solution of 
potassium cyanide or tincture of iodine. 

Silver Chloride; AgCl. This compound is always pro- 
duced and precipitated when a soluble salt of silver meets a 
soluble chloride in solution. The precipitate is at first white. 



252 

then violet, and then black. The blackening is hastened by 
the action of sunlight or the presence of organic matter. 
The change of color is due to the conversion of the chloride 
into the sub-chloride. The chloride is readily soluble in 
ammonia or in potassium cyanide. The chloride is generally 
the form to which the silver is brought for extraction from 
the ores by leaching and in some of the amalgamation pro- 
cesses. 

Reactions of Silver Salts. A silver salt in solution yields 
a white eurdy precipitate of silver chloride "whenever a solu- 
ble chloride is added. The precipitate is insoluble in nitric 
acid, blackens by exposure to light, and is soluble in solution 
of ammonia. Solutions of silverware reduced to the metallic 
state by iron, copper, zinc, and other baser metals. 

MERCURY. 

Occurrence. Mercury occurs in small quantities in the 
metallic state, but the principal ore and source of mercury is 
the natural sulphide, cinnabar HgS. Metallic mercury fre- 
quently occurs disseminated in minute globules through the 
cinnabar. The chief mercury mines are those of Idria in Aus- 
tria, Almaden in Spain, Xew Almaden in California, and other 
mines near San Francisco. 

METALLURGY OP MERCURY. 

The principle of the extraction of the mercury from the 
sulphide is simple and requires only the removal of the sul- 
phur and volatilization and condensation of the mercury. To 
accomplish this result most economically on a commercial 
scale involves an extensive plant. 

Only two methods have been employed in the reduction ; 
1st. The oxidation and removal of the sulphur of the ore by 
ignition in the air, HgS— 2 =Hg— S0 2 . 2nd, By heating the 
ore with some base as lime or iron scales by which the sul- 
phur is removed mainly as the sulphide of lime or iron. The 
second method is seldom employed and will not be described. 



253 

Roasting. The metal is now generally extracted from the 
sulphide by roasting the ore in shaft furnaces the operation 
being a continuous one. The spent ore is removed at the 
bottom and fresh ore fed in at the top of the furnace. The 
air for the oxidation of the sulphur is frequently heated 
before admission to the furnace. For this purpose the heat 
given out in the condensing chambers is most generally 
employed, the air being lead through these chambers in 
pipes. During the roasting the sulphur is converted into sul- 
phur dioxide and the mercury volatilized ; all the important 
roasting furnaces in this country are in fact shaft furnaces. 
Those which depart from the vertical shaft form consist of a 
series of parallel inclined channels built upon a natural 
slope. The channels take the place of the shaft. The ore is 
fed in at the top and the fire-place is at the bottom. 

Condensation. With the modern American continuous 
roasting furnaces the sulphur dioxide, the volatilized mer- 
cury, and other products from the furnace are conducted into 
a series of condensers so extended as to cause the condensa- 
tion of all the mercury before the products are permitted to 
escape into the air. These condensers consist of a series of 
chambers so connected that the vapors from the furnace shall 
pass through them all, the mercury being condensed and 
retained in the chambers. The chambers are so constructed 
that the mercury is gradually brought together by virtue of 
its fluidity and is removed from the chambers at necessary 
intervals. These chambers are made of iron, brick, glass, or 
wood and a plant frequently includes two or more kinds of 
chambers. Beyond the chambers proper, wooden channels 
often extend for hundreds of feet and the gases finally make 
their exit through a long flue. 

Purification of Mercury. Mercury may be purified from 
common metals by distillation. It may also be purified by 
treating it with dilute nitric acid. From mechanical im- 



254 

purities it may be freed by forcing- it through chamois 
leather; this also removes some of the metallic impurities. 
The same result is effected somewhat less perfectly, by filter- 
ing through a cone of paper with pin-hole aperture. Mercury 
in this country is put up in iron flasks at the mines, the 
flasks weighing 76.5 pounds when filled. 

Properties of Mercury. With the exception of the rare 
metal gallium, mercury is the only metal liquid at the 
ordinary temperature. As a liquid it is remarkable in that 
it neither wets nor adheres to solids, except those metals 
with which it forms alloys. Its specific gravity at C C. is 
13.59. It solidifies at-38.8° C. and boils at 357.2° C. It is a 
good conductor of heat and electricity. 

It is unaltered in air or oxygen at ordinary temperature 
but oxidizes when heated to near its boiling point, the oxide 
being again reduced when heated higher. In air containing 
hydrogen sulphide it tarnishes. When agitated with turpen- 
tine or triturated with powdered chalk or other inert sub- 
stances, it is converted into a grey powder which is thought 
to be a mixture of mercury with some oxide. This powder 
is used in making ointments and pills. Mercury forms an 
amalgam with all common metals except iron and lead. It 
adheres to platinum. 

Hydrochloric acid does not act upon mercury. Strong 
sulphuric acid has no action in the cold, but hot it attacks 
it forming mercurous and mercuric sulphates. Nitric acid 
attacks it forming mercurous and mercuric nitrates. 

Uses of Mercury. Mercury is used in the construction of 
thermometers, barometers, and other physical apparatus. It 
forms an amalgam with gold and silver and is largely used 
for the extraction of these metals from their ores. Its use 
for this purpose is improved by adding to it a little sodium 
or potassium. Many of the amalgams are used in the arts 
the most important being the amalgam with tin used in the 



manufacture of mirror glasses; this amalgam consists of 
about one-fifth mercury. The mercury is placed on a level 
surface of tin-foil and the glass carefully slid on to remove 
the excess of mercury. The plate is then subjected for 
several days to considerable pressure by which the amalgam 
is made to adhere to the glass. 

The mixed amalgam of cadmium and copper or gold, and 
of gold, silver, and tin are used in dentistry. 

Mercury in the form of vapor, or finely attenuated, will 
produce mercurial poisoning but when swallowed in sensible 
masses its injurious effects are believed to be mechanical 
rather than chemical. 

Compounds of Mercury. Mercury forms two classes of 

compounds, mercurous and mercuric. In the first it acts as 
a univalent and in the second as a bivalent element toward 
other elements. Only the most important of these com- 
pounds will be mentioned. 

Cinnabar; HgS. It has already been stated that the native 
sulphide is the source of all the mercury; the artificial sul- 
phide is largely prepared and used as a pigment. The native 
sulphide does not yield the pigment. The artificial sulphide 
is prepared in two ways, the dry and the wet. By the first 
the proper proportions of the mercury and sulphur are agita- 
ted together and the black sulphide of mercury thus obtained 
is sublimed. In the wet process the black sulphide of mer- 
cury is produced by precipitation and this is converted into 
the red sulphide by sublimation or by the long continued 
action of alkaline sulphides upon it. The red and black sul- 
phides have the same composition and the change from one 
to the other is not chemical. 

Mercuric sulphide is not soluble in either of the three 
great mineral acids at ordinary temperature. It resists the 
combined action of the air, carbon dioxide, aqueous vapor, and 
light. These facts explain the permanence of vermilion colors. 



256 

Chlorides of Mercury. There are two chlorides of mer- 
cury each of which is of considerable importance. 

Mercuric Chloride ; Corrosive Sublimate; HgCl 2 . This •sul- 
phide is produced when the vapor of mercury is burned in 
chlorine gas. On a large scale it is prepared by distilling 
mercuric sulphate with common salt, the chlorine sublimes, 
sodium sulphate being left behind, 2NaCl+HgS0 4 (heated) 
=Na 2 S04+HgCl 2 . Corrosive sublimate is quite soluble in 
hot water but much less so in cold. Its solution is extremely 
poisonous. It coagulates albumen forming with it an insolu- 
ble compound which strongly resists putrefaction. For this 
reason it is largely used by naturalists in the preparation and 
preservation of specimens. Its action on albumen makes 
this substance an antidote, if properly administered, in case 
of accidental poisoning. Wood impregnated with a solution 
of corrosive sublimate is protected from decay and the attack 
of parasites. Its use in the preservation of wood is now 
largely superseded by creasote. 

Mercurous Chloride; Calomel; HgCl. This substance is 
insoluble and is therefore produced whenever a soluble 
mercury salt meets a soluble chloride in solution. This salt 
can be manufactured by adding mercury in the proper 
proportion to the reagents used in the manufacture of cor- 
rosive sublimate when the calomel is produced instead of the 
sublimate. This is the principal salt of mercury used in 
medicine. 

Mercury Oxides. Mercury forms two oxides, Hg 2 and 
HgO, the latter commonly known as the red oxide is the 
more important. This oxide is formed when the mercury is 
highly heated in air. It is used under the name of red 
ointment and when thoroughly incorporated with certain 
ingredients constitutes a poisonous ointment sometimes used 
to destroy the parasites which affect animals. It is prepared 
for this purpose by decomposing the nitrate of mercury by a 



257 

gentle heat or better by adding a little mercury and de- 
oxidizing the nitrate, Hg(N0 3 ) 2 + Hg 2 = 3HgO+N 3 3 . The 
oxide parts readily with its oxygen and is therefore some- 
times used as an oxidizing agent in the laboratory. 

PLATINUM. 

Occurrence. No compound of platinum with a non- 
metallic element has been found in nature. It is always 
found in the metallic state but always alloyed with the other 
metals. The metals usually present belong to the platinum 
group and are rhodium, iridium, osmium, ruthenium, and 
palladium; these metals usually occur alloyed with each 
other and with the platinum. The platinum metals are 
found in alluvial deposits similar to the deposits containing 
gold, indeed gold is frequently present. 

Most of the platinum is obtained from the Russian de- 
posits in the Ural Mountains, near Goroblagodat; some 
comes from Brazil, Peru, Colombia, Borneo, and it has been 
found in the United States, Canada, and Australia. The 
platinum alloys generally occur in small grains distributed 
through the sands from which it is separated by washing. 
The process of separating the platinum from the associated 
metals is largely a chemical one, it was formerly entirely so. 
The separation in this process was brought about by the 
action of aqua regia upon the native alloy and depends 
partly upon the relative action of the strong and weak acids 
upon the different metals and partly upon the different 
properties of the chlorides produced. The platinum has also 
been separated by smelting the ore with galena. The lead 
forms an alloy containing nearly all the platinum from which 
it is separated by cupellation. 

Properties of Platinum. With the exception of osmium 
and indium platinum is the heaviest of the elements, its 
specific gravity referred to water being 21.5. It is 23400 
times as heavy as hydrogen. It is the most infusible of the 



258 

metals. It can be readily melted by the oxy-hydrogen name 
and by this means it can be made into vessels. It is not 
affected by the air at any temperature, nor do any of the 
acids singly attack it at common temperature. Concentrated 
sulphuric acid at high temperature acts slightly upon it. It 
is very malleable and ductile and at high temperature (white 
heat) is weldable. It possesses the power of causing the 
combination of oxygen with other gases or vapors. 

It is dissolved by aqua regia, the fused caustic alkalies 
attack it, as do phosphorus, sulphur, arsenic, and carbon at 
high temperature. It readily alloys with lead and other 
easily fusible metals. Care should be taken that these sub- 
stances be not heated highly in platinum vessels. 

The action of platinum upon gases may be shown by 
holding a piece of thin platinum foil in the flame of a 
Bunsen burner until it is red hot, then if the gas be turned 
off and then be turned on quickly again the escaping gas will 
keep the metal at a red heat and may even relight it. This 
result is brought about by the influence of the metal in caus- 
ing combination between the gas and the oxygen of the air. 
The temperature of the foil may be too low to emit any light 
when the gas is turned on, but the oxidation occurring at its 
surface soon brings it to redness. Spongy platinum (obtained 
by decomposing the ammonia- chloride of platinum) pos- 
sesses this actuating power to a higher degree than does the 
foil. 

Dobreiner's automatic lamp is lighted by means of spongy 
platinum. This apparatus consists of an alcohol lamp in 
connection with a little automatic hydrogen generator. By 
pressing a lever a jet of hydrogen flows out and falls upon 
some spongy platinum. The oxidation that ensues rapidly 
raises the temperature until the vapor of alcohol from the 
lamp-wick near the metal inflames. This action of the metal 
was for a time made use of in the manufacture of acetic acid. 
The spongy metal caused the rapid transformation of the 



259 

alcohol into acetic acid by inducing the oxidation of the 
alcohol. 

The precipitated form of platinum commonly called plati- 
num black possesses this power to a still higher degree; 
hydrogen is instantly ignited by falling upon it. This form 
of platinum is capable of absorbing 800 times its volume of 
oxygen and it absorbs and condenses considerable quantities 
of other gases. The oxidation caused by it is probably in 
some cases due to the greater physical contiguity of the 
gases produced by the condensation. 

Platinum is employed in the form of wire, foil, dishes, cru- 
cibles, forceps, tongs, retorts, and other laboratory appa- 
ratus. Its small coefficient of expansion permits it to be 
fused into glass without subsequent cracking. Platinum is 
used in large vessels for retorts and coolers in the purifica- 
tion of sulphuric acid. 

Compounds of Platinum. Platinum forms two classes of compounds 
the platinous and the platinic — in the first it plays the part of a dyad 
and in the second of a tetrad. The most important of the platinic 
compounds is the platinic chloride, perchloride, PtCl 4 . It may be 
prepared by dissolving platinum in aqua regia. This salt is of value in 
the laboratory because it forms slightly soluble double chlorides with 
the chlorides of the alkali metals and with certain organic hydro- 
chlorides and thus aids in detecting and separating these bodies. 

Other Metals of the Platinum Group. As already stated, the other 
metals included under this head are palladium, iridium, osmium, rho- 
dium, and ruthenium and they are generally found in association with 
platinum, alloyed with each other and with it. These metals resemble 
platinum in their unchangeable nature in air. Iridium is the most use- 
ful of this group. It is a hard steel like metal and is used for knife 
edges in delicate balances and for similar resisting surfaces. It gener- 
ally increases the hardness of its alloys. Its alloys with platinum are 
important. The most refractory platinum vessels contain some iridium . 
These alloys were adopted by the Committee on International Stand- 
ards for making standard weights and rules. 

Palladium is the most fusible of the group, its fusing point being 
between 1500° and 1700° C. Osmium is the heaviest of the elements vet 
discovered, its specific gravity being 22.39 to 22.42. 

Osmium forms a volatile tetroxide which is very poisonous. The 
native alloy of osmium and iridium is used to a limited extent for hard 



260 

wearing surfaces; this alloy is found most abundantly in Russia, Cali- 
fornia coming next in order of production. 

Palladium possesses the power of absorbing and condensing gases 
to a remarkable degree and the metal has been used to a limited extent 
for wearing surfaces in philosophical apparatus. 

The salts of this group have found no useful application. . 

GOLD; Au. 
Occurrence. G-old occurs widely distributed iu uature 
though iu small quantities. It is nearly always found pure 
or alloyed with other metals but occasionally combined with 
tellurium. The natural gold is most usually alloyed with sil- 
ver but sometimes with copper and other metals. Gold prin- 
cipally occurs in four ways ; 1st, Disseminated through the 
gangue of quartz veins; 2nd, In alluvial deposits ancient or 
modern; 3rd, To these modes of occurrence of gold must now 
be added that of the South Africa gold fields where the metal 
is disseminated through "reefs " which were originally shal- 
low marine deposits, but now form part of the mainland far 
from the shore ;* 4th, Gold also occurs in small quantities in 
ore deposits of other metals. 

METALLURGY OF GOLD. 

The sources from which gold is obtained in commercial 
condition come under three heads, 1st, From the auriferous 
ores of the metals; 2nd, From auriferous quartz veins; 3rd, 
From sedimentary deposits, alluvial or marine.* The pro- 
cesses by which the gold is obtained from these sources may 
be limited to four as follows: 1st, Smelting; 2nd, Amalgama- 
tion; 3rd, Leaching; 4th, Simple washing by water. It is 
thus seen that the processes employed except the last bear 
the same names as those employed in the metallurgy of silver 
and the general method of treatment and the principles in- 
volved are very similar. 

*Gold has also been found in the sands of certain sea beaches of the 
present day, notably in California, Oregon, and Australia, and it is 
known to be present in minute quantity in sea water. At one time 
attempts which were partially successful were made to obtain gold 
from the beach sands of our western coast. 



* 261 

Smelting. This process is applied only to the gold from 
the first source and includes all that gold obtained in the 
smelting of argentiferous copper and lead containing gold. 
These processes have been described and it is only necessary 
to state here that the gold after the smelting, remains with 
the silver and is separated therefrom by acids or by elec- 
trolysis. Gold is thus obtained in considerable quantity at 
many smelters in this country — notably those in Montana, 
Arizona, and Colorado. The gold is, however, not the prin- 
cipal product of these smelters. 

Gold ore from quartz veins is sometimes crushed and 
smelted with lead or copper ores, for the purpose of remov- 
ing the gold, but no additional principle is involved to those 
already described under the smelting for these metals; but 
the gold from the quartz veins is almost always separated in 
the manner now to be described. 

Gold from Quartz Yeins. In obtaining the gold from 
quartz veins there are usually involved two distinct pro- 
cesses: 1st, Amalgamation; 2nd, Leaching or lixiviation. To 
secure as much gold as possible from the ore it is generally 
subjected in succession to treatment by both processes. 
Occasionally only the first is employed, but the leaching 
process is often employed alone. These processes are very 
similar to the corresponding processes for obtaining silver — 
they will be briefly outlined. There are several distinct 
steps in each of the above processes, but the chemical prin- 
ciples involved are simple. The gold bearing rock is first 
broken and then stamped to a fine state of division in 
"stamp batteries." These "batteries" are essentially similar 
to those described for the stamping of silver ores and they 
consist of an iron mortar and a stamp; the latter are iron 
rods shod with steel and are lifted and dropped by 
machinery. They weigh from 700 to 1000 pounds. By these 
stamps the ore is crushed until it is fine enough to pass 
through the perforated screens in the side of the mortar. 



The proper quantity of water is admitted to the mortar and 
carries the crushed ore through the screens. Gold mills are 
always wet stamping. 

Amalgamation. The amalgamation may begin in the 
"batteries'" or not tuitil the pulp has passed through the 
screens. When amalgamation begins in the "batteries" the 

mortars are usually lined at the ends and on one or both 
sides with amalgamated copper plates and mercury is 
charged into the "battery." The mercury amalgamates the 
gold and a large part of it is caught in the copper plates and 
inside the "battery." Another portion of the gold is caught 
by appliances outside the "battery." These connivances 
consist of inclined aprons or tables covered with amalga- 
mated copper plates, frequently arranged in descending 
steps — the>e plates begin just in front of the screens. The 
pulp after passing through the screens is carried by the 
water over the outside copper plates, which catch more of 
the free gold. The amalgamated copper plates are cleared 
off at intervals and the amalgam "retorted" to separate the 
gold: sometimes the amalgam is washed by grinding in a 
pan before "retorting." 

The pulp after leaving the copper aprons is made to flow 
over blanket-sluices. These sluices are covered with specially 
prepared mill blankets. The nap of these blankets arrests 
still another portion of the gold, while most of the sand and 
lighter minerals are carried over them. These blankets are 
removed at intervals and washed and the washings are amal- 
gamated in a special apparatus. This amalgam is "retorted" 
to separate the gold. "When amalgamation begins in the 
"battery" the blanket sluices are less generally used. 
Whether the blanket sluices are used or not the sands or 
"tailings" carried away by the water are often subjected to 
further treatment. These "tailings" may be treated by 
amalgamation in grinding pans, but they are generally too 



263 

impure to be treated in this manner and are subjected to the 
next process to be described. 

Chlorine Leaching. Preliminaries. This process is seldom 
in this country applied directly to the ores from the mine but 
is used to obtain the gold which is not caught in the amal- 
gamation operations and which remains with the sands or 
"tailings." As these sands contain only a small per cent of 
gold, the first step usually taken is to separate mechanically 
as far as practicable the gold bearing material from that 
which carries no gold. This operation is termed "concentra- 
tion " and is accomplished by the mechanical action of water 
upon the gold bearing material. The object of "concentra- 
tion" may be stated to be, to get out of comparatively poor 
material a comparatively rich one. The process of "con- 
centration" is generally applied to the "tailings" though it is 
sometimes used to convert a poor ore into a richer one 
before it is subjected to other treatment. 

The gold to which the leaching process is applied is in the 
metallic state but so intimately associated with other min- 
erals that the mercury has failed to reach it in the amal- 
gamation. The minerals most commonly thus associated 
with gold in the " concentrated tailings " are sulphides of iron 
and other metals, the former usually constituting the larger 
portion. The next step is to roast the "tailings" to convert 
all the baser metals present into oxides. 

Chlorination. The roasted ore is next subjected to the 
action of chlorine by which gold chloride is formed. The 
chloride of gold is dissolved out of the chlorination vat by 
lixiviation with water and the solution received in a precipi- 
tating tank. The gold is precipitated from the solution in 
the metallic form by the addition of ferrous sulphate; the 
precipitated gold needs only to be fused. The above met hod 
of chlorination is known as Platner's process. 

Cyanide Leaching. The leaching of "concentrated" ores 
as well as "tailings" which are comparatively free from 



264 

sulphides, is now largely accomplished by treating- with a 

weak solution of potassium cyanide. This in the presence of 

oxygen forms a soluble compound with the gold from which 

the metal may be recovered by precipitation by metallic zinc 

or by electro-deposition. 

The principles employed and the general methods pursued in the 
amalgamation and leaching processes are outlined above, but the 
number of operations and the details of each vary with the kind and 
nature of ore. With some varieties of gold quartz so nearly all the 
gold is obtained by amalgamation that the "tailings" are not worth 
working. With some ores "concentration" may precede amalgama- 
tion instead of the reverse as described above. Sometimes the 
amalgamation process is preceded by the roasting of the ores and 
occasionally the ore is such that the leaching process is not preceded by 
amalgamation. When the ores to be leached by chlorine are rich in 
silver there is usually added a little salt to the roasting charge and the 
silver is converted into the chloride. The silver chloride can be dis- 
solved out before the ore is subjected to chlorination. Platner's 
chlorination process has been modified in this country by Mears so that 
the chlorine is delivered under pressure into revolving amalgamating 
barrels. The gas acting under pressure and the agitation and friction 
of the ore give some marked advantages to this modification but there 
were at the same time some disadvantages, one of the most marked 
beingthe escape of some of the compressed chlorine. Theiss improved on 
the Mears' method by generating the chlorine in the amalgamating 
barrel itself, though under less pressure the nascent chlorine was found 
to be very active and the Theiss barrel method has found extensive 
application in our western country. 

Gold from Sedimentary Deposits. A large proportion of 
the world's supply of gold has been obtained from sedi- 
mentary deposits. In this country the gold from this source 
is limited to alluvial deposits but in the rich mines of South 
Africa which have recently come into such prominence, the 
gold is found in the marginal sea deposits of previous ages 
which are now tilted and displaced and lie far inland. We 
shall first speak of the gold from the alluvial deposits of this 
country. 

Placer Mining. The gold from this source in this country 
is obtained by what is called placer mining. The placer 
deposits exist in the sands along the beds of the present 



265 

streams or in the sands and gravels which now occupy the 
beds of channels and banks of extinct streams. The gold is 
separated from the sands mainly by the action of water. 

When gold was first discovered in California in 1848 a 
large amount of it was obtained by simple pan- washing. 
This process was followed by cradle washing and then by 
sluice working. As the shallow placers were exhausted and 
the working was extended to the deep placers of former river 
channels, hydraulic mining was developed. By this means 
it became possible to economically wash very large masses 
of earth, in several places several million parts of earth were 
worked to obtain one of gold. The large amounts of water 
and earth thus handled required very extensive appliances. 
The sluices were made from a few hundred feet to several 
thousand feet long. The great difference between the specific 
gravity of the gold and the sands (19.3 and 2.6) rendered 
separation by washing possible, but amalgamated copper 
plates, riffles and mercury were used in the sluices to more 
perfectly catch the gold as the operations were extended. In 
these deep placers the richest sands were generally near the 
bed rock of the stream and sometimes were so consolidated 
that they had to be "weathered" or crushed before washing. 

In some places the deep placer deposits extended under 
rock formations that could not be removed. This led to drift 
mining. The auriferous sands from these mines were often 
found so consolidated that they had to be subjected to the 
milling and amalgamation process already described. ( 

Africa Gold Mines. The great mines of the Rand in South Africa 
deal with gold occurring; in a hard conglomerate which was originally 
a marginal sea-deposit. These deposits were tilted and displaced and 
now form part of the interior highlands of the country. The sheets in 
which the gold occurs are called "banket reef." These reefs are mined 
exactly as are quartz veins. The ore is crushed in stamps and treated 
by the amalgamation process above described. The amalgamation is 
begun in the mortars. The "tailings" are "concentrated" and sub- 
jected to the chlorination or cyanide process of leaching as already 
described, the cyanide process being the more common. 



266 

Properties of Gold. Gold is a metal of great antiquity 
and has from the earliest times been esteemed a precious 
metal. In a pure state it is only about as hard as lead. It 
is the most malleable and ductile of metals. Its specific 
gravity is 19.3. For commercial purposes gold is always 
alloyed with some other metal to increase its hardness and 
durability, silver and copper being the metals most generally 
employed for this purpose. The gold coin of the United 
States is nine-tenths gold, and one-tenth copper alone or an 
alloy of copper and silver. The purity of gold is generally 
indicated by carats; pure gold is 24 carats fine. Grold of 18 
carats is only three-fourths fine. On account of its great 
malleability gold leaf can be made exceedingly thin. 

Gold is not affected by the atmosphere or moisture and 
does not tarnish. It is not acted upon by any of the ordinary 
acids but it is attacked by aqua regia or free chlorine. Com- 
mon gold alloyed with copper may be made to present a pure 
gold surface by heating and oxidizing the copper and dis- 
solving it out with sulphuric or nitric acid. The uses of gold 
are too well known to require mention. 

COMPOUNDS OF GOLD. 

Gold Chloride; AuCl 3 . The most important of the inorganic salts 
of gold is the gold chloride, AuCl 3 . It can be prepared by acting upon 
gold with aqua regia. The chloride is very easily reduced to the metal- 
lic state. Organic matter generally, and nearly every substance capable 
of combining with oxygen will reduce it. The property of the salt 
together with the permanency of the deposited metal renders the 
chloride useful in photography. 

Oxides and Sulphides. Three oxides of gold have been obtained but 
they are of no practical importance. Several combinations of gold 
with sulphur have been obtained but their compositions are not well 
determined and they are not of practical importance. The Purple of 
Cassius produced when stannous and stannic chlorides are added to 
dilute solutions of gold is used in enamel painting and in coloring 
glass. It gets its name from the discoverer, Andreas Cassius of Leyden. 
The exact composition of this substance is not known but it contains 
gold, tin, and oxygen. 



ORGANIC CHEMISTRY OR CHEMISTRY OF 
THE CARBON COMPOUNDS. 



CHEMISTRY OF THE CARBON COMPOUNDS. 

The term " organic chemistry " was formerly used to 
denote the chemistry of compounds found in the bodies of 
plants and animals. It was originally thought that these 
compounds could only be produced in living organisms, 
animal or vegetable, and that their production was due to the 
vital forces which were different from the chemical forces 
artificially brought into play in the laboratory. This view 
led to the separation of chemistry into two branches of 
organic and inorganic — the latter including the chemistry of 
those compounds whose existence in no way depended upon 
the "vital forces." 

The assumption as to the action of the different forces in 
the organic and inorganic worlds was rendered untenable 
when it was shown that many organic compounds could be 
formed by the direct combination of elements or the trans- 
formation of inorganic compounds. The preparation of 
urea accomplished in 1828 by Wohler, was the first step in 
the artificial formation of organic compounds from their 
inorganic constituents. Many organic compounds of great 
complexity have since that date been built up from the 
elements themselves and it is now universally recognized 
that the chemistry of the organic compounds is but a part of 
the general science of chemistry. 

Organic compounds all contain carbon, and organic chem- 
istry is really the chemistry of the carbon compounds but on 



268 

account of the large number of such compounds it is con- 
venient to study them separately rather than in connection 
with the element carbon. For the sake of convenience the 
division of chemistry into two branches is still generally 
retained, though the original reasons for the separation have 
been shown to be erroneous. 

There is however a distinction between organic compounds 
and organized bodies. The former have a definite chemical 
composition, many of them can be produced artificially and 
possess definite chemical and physical properties ; organized 
bodies consist of mixtures of definite compounds and have 
only been produced under the influence of vitality. The 
chemical relations of the organized bodies and the life pro- 
cesses which go on in them, are treated under physiological 
chemistry. 

CLASSIFICATION OF CARBON COMPOUNDS. 

The compounds of carbon outnumber the compounds of 
all the other elements taken together. The elements most 
usually combined with the carbon in these compounds are 
hydrogen, oxygen, and nitrogen. A large number contain 
only carbon and hydrogen; a still larger number consist of 
carbon, hydrogen, and oxygen; many consist of carbon, 
hydrogen, and nitrogen ; and still others of carbon, hydrogen, 
oxygen, and nitrogen. In addition to the four elements 
named, sulphur and phosphorus frequently occur. In the 
carbon compounds from organic sources the above named 
are the elements generally found, but almost all the elements, 
metals and metalloids have been artificially introduced as 
constituents of these compounds and some of the metals are 
found in the natural compounds. The classification of carbon 
compounds like all other classifications, is based upon simi- 
larity of properties and characteristics of the bodies grouped 
together. 

The nature of the carbon compounds permits a much 



269 

more perfect classification than is possible in the inorganic 
chemistry. The members of the same class and the different 
classes are derivable from each other by comparatively 
simple reactions. 

The system of classification includes nearly all artificially 
prepared carbon compounds and the greater proportion of 
those produced in living bodies, but there are many com- 
pounds formed in the vital processes of plants and animals 
whose chemical relations are not sufficiently known to permit 
their classification, such are the alkaloids and the albumi- 
noids yet to be mentioned. 

The compounds of carbon are usually grouped into thirteen classes 
based upon their rational or constitutional formulae, that is the 
formulae which indicate the radicals that compose the compound. 
There are other classes whose rational formulae are not made out, 
based upon certain similar characteristics. 

There are a great many carbon compounds which contain 
only carbon and hydrogen and most of the other well defined 
carbon compounds can with reason be considered as de- 
rived from these, so that the compounds of carbon in- 
cluded under the term "organic" are generally derivatives 
of those containing only carbon and hydrogen known as 
hydrocarbons. It is not the purpose of this text to consider 
the varied relations between the different classes nor between 
the members of the same class of the carbon compounds, 
and the classification of the compounds described will only 
be referred to when such reference helps to define and 
elucidate the characters which it is sought to set forth. 

The most general divisions of the carbon compounds 
which include all those just referred to, are the fatty and 
aromatic groups. The bodies which make up the first group 
are derivatives of the hydrocarbons whose general formula 
is C n H 2 n+2 (paraffin series) ; the second group is derived 
from the benzene series whose general formula is r„H,>n-«. 
These two groups, fatty and aromatic, are very convenient 
for general reference. 



270 

STRUCTURAL OR CONSTITUTIONAL, AND RATIONAL 
FORMULAE. 

The basis for the classification of organic compounds is 
usually partially represented in their chemical formulae. 
Such formulas have already been referred to as structural 
formulae but it will be of convenience hereafter to state some- 
what more fully the significance of these formulae. By the 
careful consideration of the changes and the behavior of any 
chemical compound under a large variety of dissimilar cir- 
cumstances it is believed that the order of combination of 
the atoms in the molecule in many such compounds has been 
determined. A formula which gives the fullest knowledge 
as to the constitution of a compound is called its structural 
or constitutional formula. By such formula it is intended to 
indicate the connection between the atoms in a molecule. It 
should be kept in mind that the representation of the 
formula on paper is of no importance as the formulae are 
intended to express the manner of combination and not the 
actual positions of the atoms themselves. Thus the con- 
stitutional formula of methyl-alcohol is determined to be 
H 

H— C— H H O 

and of acetic acid is h— c— c— o— H. 

1 I 

H— C— H. H 

I 
H 

A rational formula is one that from the way in which it 
is written, indicates the manner in which a compound breaks 
up or is formed under certain conditions, or shows the rela- 
tions of allied compounds to each other. It is an abridged 
constitutional formula which indicates certain relations not 
shown in an empirical or molecular formula; or it is a mole- 
cular formula so written as to indicate certain chemical 
relations of the compound. Thus the formula for acetic acid 
may be written C 2 H 3 2 H to show that the acid is monobasic 



271 

or it may be written C 2 H 3 0,HO which indicates the origin of 
the acid from certain salts. Since a compound may split up 
into different groups or radicals or may be formed in differ- 
ent ways the same body may often have a number of rational 
formulae each of which indicates certain characters under 
certain conditions. This fact has already been illustrated in 
the supposed constitution of certain inorganic salts, but 
owing to the larger number of atoms in many organic com- 
pounds the principle of resolution into rational formulae is 
much more frequently possible. 

Isomerism and Polymerism. Isomerides or isomeric 
bodies are those bodies which have the same percentage com- 
position and molecular weight but show different properties. 
Those isomerides which differ in physical properties but 
whose transformation under the action of the same agents 
closely resemble each other are called "isomers." Those 
isomerides which exhibit dissimilar transformation under 
similar circumstances are called "metamers." The phenome- 
non of isomerism is only explicable upon the supposition 
that the arrangements of the atoms in the molecules are 
different. 

Polymeric bodies or "polymers" are those which have the 
same percentage composition but different molecular weights 
and consequently different molecular formulae. The carbon 
compounds furnish many examples of isomers, metamers, 
and polymers. 

HYDROCARBONS. 

Of the carbon compounds the simplest are those contain- 
ing only hydrogen and carbon and from these, as already 
stated, most of the others can be derived. The hydrocarbons 
furnish several series of compounds and each series under 
the action of reagents yields derivatives so that the possible 
number of carbon compounds is very great. These com- 
pounds frequently exhibit a characteristic not common among 
inorganic bodies— their molecules contain a large number of 



272 

the atoms of the elements which enter them, thus rendering 
possible a great number of isomers. 

SATUEATED HYDEOCAEBONS. 

Paraffin Series; Formula C n H2n+2. The only hydrocarbon 

containing but a single atom of carbon is methane or marsh 

gas. Carbon being a tetrad and hydrogen a monad it is 

evident that on the theory of valency the constitutional 

formula of marsh gas must be represented thus 

H 

I 
H-C— H. 

I 
H 

indicating a saturated compound or one in which there are 

no free units of valency. A consideration of the formula 

above given will show that the relation between the number 

of atoms of the two elements is such that there are no free 

affinities. The hydrocarbons of this series can not form 

compounds with other bodies except by substitution, one or 

more of the atoms of the molecule must be removed to effect 

the introduction of others. Since hydrogen is a monad and 

can not act as a connecting atom, it is evident that on the 

theory of valency the carbon atoms in hydrocarbons must be 

connected directly to each other. The different ways in 

which the connection may be made and yet satisfy all the 

affinities of each element is thought to explain the frequent 

occurrence of "isomers." In the saturated hydrocarbons it is 

thought that no two carbon atoms are held together by more 

than one combining unit of each atom. 

Methane or marsh gas is the lowest member of this series, 

the others containing more than one atom of carbon. The 

formulse of the consecutive members of the paraffin series 

differ from each other by CH 2 , the first four are, methane 

CH 4 , ethane C 2 H 6 , propane C 3 H 8 , and butane CJLo. Such a 

series is termed an homologous series. The highest known 

member of this series contains 35 atoms of carbon. The 



273 

members of the series up to those containing four atoms of 
carbon are gases ; from four to sixteen they are liquid at 
ordinary temperatures; those containing a greater number 
than sixteen atoms of carbon are solid. 

Many of the hydrocarbons of the paraffin series occur 
abundantly in nature. The occurrence of methane as marsh 
gas and fire-damp has already been referred to. 

Petroleum. The great natural source of this group is the 
petroleum oil which is found most abundantly in this country 
and in Russia — it is also found in several other countries. 

American petroleum consists almost entirely of the paraf- 
fin hydrocarbons, some of the benzene group are present in 
small quantities. The Russian petroleum contains a consid- 
erable per cent of the benzene hydrocarbons and their deriv- 
atives. The petroleums are mixtures of the various members 
of these hydrocarbon series which are separated from each 
other by fractional distillation — a large number of valuable 
products is derived from them. 

In this country the oil wells are connected by pipe lines 
with the refineries at New York, Baltimore, Pittsburgh, Cleve- 
land, and Buffalo. The lines in some cases are over three 
hundred miles long and the oil is forced by pumps through 
the pipes from the wells to the refineries. 

At the refineries the oil is subjected to fractional distilla- 
tion. The products which first come off as the temperature 
rises, are of course the gaseous products. The more easily 
condensible of these are collected, liquefied by pressure, and 
used to produce cold by evaporation — in the manufacture of 
ice, etc. This product is mainly , composed of CJLo butane 
and is called cymogene. The names of the commercial prod- 
ucts vary at different places — some of the more important in 
the order of the boiling points are Rhigolene used as an an- 
aesthetic, Petroleum ether used as a solvent for rubber, Gaso- 
lene used for enriching coal gas, Naphtha used as the working 
substance in naphtha engines. Benzine used as a solvent is 

18 



274 

largely substituted for turpentine and comes off between 120° 
and 150° F. ; it is entirely different from benzene, the latter not 
belonging to the paraffin series. Kerosene is the product 
which distills over between 150° and 300° F. and is the liquid so 
largely used as a burning oil. It is purified by agitating with 
acid and in alkaline solution before it is put upon the mar- 
ket. There are many grades of this oil depending upon the 
color and fire test to which the oil is subjected. The fire 
tests are in some cases fixed by law and differ in different 
places. An oil which when heated in an open vessel to 
100° F. does not give off vapor enough to ignite when a 
flanie is brought near its surface, is safe under ordinary 
conditions of use. 

The residue of the crude oils after distilling off the kero- 
sene, is subjected to still higher temperature and from it are 
obtained the lubricating oils and the solid paraffins. The 
lubricating oils are daily increasing in importance and are 
now used in immense quantities. The softer of the solid 
paraffins are called vaselines, of which there is a number of 
varieties. The more solid wax-like paraffins are present only 
in small quantities in the American petroleum, less than 
three per cent ; they reach ten per cent in the Burmah petro- 
leums and are very much more in the petroleum from the 
shores of the Caspian. 

The greater proportion of the solid paraffin is prepared 
from the products obtained from the distillation of carbon- 
aceous shales. Scotland is the centre of the industry. In 
G-ermany and Austria large quantities of paraffin are ob- 
tained by the distillation of brown coal or lignite. These 
coals and shales yield also burning and lubricating oils simi- 
lar to those from petroleum. 

Paraffin is tasteless and without odor, insoluble in water 
but freely soluble in ether. It is largely used as a substitute 
for sulphur in dipping matches; it is used in the manufac- 
ture of candles, in water-proofing and finishing cloths, and 



275 

as an insulator in electrical apparatus. It has also been 
applied to preserve food from deterioration. 

Native solid hydrocarbons are found and known under 
the name of ozokerite. It is used in Europe in the manu- 
facture of candles. It closely resembles paraffin but is 
thought to contain a smaller per cent of hydrogen. 

The petroleum industries of the United States are of 
immense extent and of vast importance. The burning 1 and 
lubricating oils furnish one of the largest items of export. 
The refined oils are exported in tank steamers and a number 
of these steamers is engaged in such service running between 
American and European ports. 

UNSATUKATED HYDROCARBONS. 

All hydrocarbons which do not have the formula CnHsn+2 
are found to be capable of uniting directly with certain other 
bodies without the removal of any of the constituent ele- 
ments, it is therefore assumed that in these hydrocarbons 
some of the carbon atoms are linked together by more than 
one unit of valency of each, hence ethene may be indicated 

thus 

H— C-C— H 

I I 
H H 

and acetylene thus H — C = C — H. In the saturated com- 
pounds no atom is connected to any other by more than one 
unit of valency of each ; in the unsaturated two atoms may 
be connected by more than one unit of each. It is readily 
conceivable that in these compounds the atoms which arc 
connected by more than one combining unit of each nun- 
extend this excess of affinity to other bodies, thus forming 
new compounds without any change of elements. 

define Series. These are unsaturated hydrocarbons 

whose general formula is CnIT>„. The lowest member of the 
series is olefiant gas, ethene, or ethylene C2H4. The series 



276 
« 
is an homologous one and results by the successive addition 
of CH 2 . 

The first three members of the series are gaseous — most 
of the remainder are liquid, but the four highest members 
are solid. The members of this series resemble in properties 
the corresponding members of the paraffin series — the boiling- 
points of the liquid members which have the same number of 
carbon atoms lie very close together. This series is obtained 
from petroleum oil and by the destructive distillation of car- 
bonaceous matter. Ethylene the lowest term of the series, 
has already been mentioned m connection with carbon — the 
highest member contains thirty atoms of carbon. 

Acetylene Series. The general formula for the series is 

CnILn-2. Acetylene is the lowest member of the series and 

the homologues differ consecutively by CH 2 . This series, 

as the two preceding, consists of gases, liquids, and solids. 

Acetylene is the only hydrocarbon that can be produced 

artificially — its production and uses were described under the 

element carbon. 

The terms of the olefine series differ from the corresponding: terms 
of the paraffin series by two hydrogen atoms and the acetylene series 
from the olefine series in the same manner; the hydrogen in proportion 
to the carbon growing less in the series in the order named. The latter 
two series may therefore be considered as derivatives of the paraffin or 
methane series. 

4 

Benzene Series; Aromatic Hydrocarbons. The general 
formula for the series is CnH 2n -6 where "n" is a whole number 
not less than six. The homologues differ successively by 
OIL. On account of the fragrant odor of some of the benzene 
derivatives they were formerly termed aromatic hydrocarbons, 
but equally fragrant odors are found among the methane 
derivatives, hence the term is no longer strictly applicable. 

Benzene. The lowest member of the series is benzene 
C 6 H 6 . This body is the basis from which a large number of 
organic compounds may be derived. Benzene is produced 



277 

in the destructive distillation of many organic substances, it 
is also found in petroleum. It is present in considerable 
quantity in the more volatile portion of coal-tar oil and this 
is the source from which it is principally obtained. The light 
oil from coal tar is subjected to fractional distillation by 
which the benzene is separated and purified. 

It is when pure a thin limpid liquid with an odor sug- 
gestive of coal gas. It solidifies at 0° C. It is insoluble in 
water but mixes with alcohol and ether. It dissolves sul- 
phur, phosphorus, iodine, and many fats and resins which 
are insoluble in water. It is manufactured in large quantity 
for conversion into aniline from which are obtained many 
beautiful and useful dyes. Its vapor constitutes one of the 
illuminating constituents of coal gas. 

Terpene Hydrocarbons. The empirical formula of this 
group is C 5 H 8 . They are volatile oils existing in certain 
plants; they have not been formed by artificial processes. 

Turpentine oil is the most important member of the ter- 
penes, its formula is GoH 16 . It exists in the wood, bark, and 
leaves of many coniferous trees and is generally prepared by 
distilling the thick juice which is obtained by tapping 
(making incisions into the bark) the trees. This juice is a 
mixture of turpentine oil and resin. In this country turpen- 
tine is principally obtained from two varieties of the pine the 
industry being most largely developed in North Carolina. 

Turpentine oil when pure is colorless and mobile — it has a 
penetrating and disagreeable odor. Its boiling point is 158- 
160° C. Its specific gravity is .86. It is but slightly soluble 
in water but dissolves in strong alcohol, ether, and carbon 
disulphide. It burns with a smoky flame. It dissolves 
idione, sulphur, phosphorus, caoutchouc, resins, and many 
fixed oils. The consumption of turpentine oil or spirits in 
the preparation of paints and varnishes is very extensive. 

There is a large number of other essential oils belonging 
to this group which have the same empirical formula and 



278 

many of them the same molecular formula as turpentine oil. 
Such bodies are the oils of lemon, juniper, orange, birch, 
etc. These oils are generally obtained by distilling the 
leaves, flowers, seeds, or other vegetable products with water, 
or by passing a current of steam through these products. 
The boiling points of the oils are much higher than that of 
water but they readily distil with aqueous vapor. When the 
vapors condense the greater portion of the oil forms a layer 
on the surface of the water and may be entirely separated 
by shaking the water with ether or saturating it with salt. 
The ether dissolves the oil and can be separated by distilla- 
tion. The salt causes the oil to separate. In some of the 
more delicate perfumes the distillation is accomplished in a 
vacuum or the oil extracted by pressure or dissolved out by 
carbon disulphide. These oils when not isomeric with tur- 
pentine oil are mixtures of hydrocarbons, having the slame 
percentage composition, with compounds of carbon, hydro- 
gen, and oxygen. By exposure to the air they slowly absorb 
oxygen and lose their liquid state. They mix in all propor- 
tions with linseed, whale, and other fixed oils. The greasy 
stain communicated to paper by a volatile oil can be entirely 
removed by heating, which is not the case if it contains a 
fixed oil. 

Camphors. The camphors are crystalline bodies closely related to 
the t\rpenes, from which they appear to be formed by oxidation. 
Common camphor is obtained by distilling' the chopped wood of the 
camphor laurel of China and Japan. It has been produced by the 
artificial oxidation of several terpenes. Camphor is very slightly solu- 
ble in water but readily so in alcohol and ether. It burns with a 
smoky flame. Its formula is C 10 H 16 O. 

Resins and Balsams. The resins are closely related to the terpenes 
and appear to result from their oxidation. They are not definite com- 
pounds but mixtures, the essential ingredients being certain resin acids, 
which are rich in carbon and hydrogen and contain some oxygen. The 
resins are all, with unimportant exceptions, of vegetable origin. 

Common resin or colophony is the best example of the class. It is 
the substance remaining when crude turpentine is distilled and the oil 
of turpentine expelled. The resins are very widely distributed in the 



279 

vegetable kingdom. They are insoluble in water but dissolve in 
alcohol. 

There is a large number of resins used for industrial purposes. 
Shellac is employed in the manufacture of hats and is the chief constitu- 
ent of sealing-wax. The many varieties of varnish are prepared by 
dissolving resins in alcohol. Mastic, dammar-resin and sandarac are 
some of the common varnish resins. Amber and copal are fossil resins, 
though the latter is also obtained direct from the trees. 

Balsams. These are natural mixtures of resins and essential oils 
and sometimes acids. They are of different degrees of consistency and 
by keeping the softer kinds become harder. 

Caoutchouc — India Rubber. Caoutchouc is closely allied 
to the terpenes. The substance of which it is mainly com- 
posed has a formula which is some multiple of C 5 H 8 . The 
caoutchouc of commerce is obtained from some half dozen 
different genera of tropical plants including 1 certain climbing 
plants as well as trees. If the source is a tree an incision is 
made in the bark and the exudation collected in earthen or 
tin cups. As these receptacles are filled they are emptied 
into larger vessels all of which are brought together at some 
favorable location. The rubber juice is now brought to a 
solid form by evaporating it from a sort of bat or shovel 
which is dipped into the liquid juice and held over a fire 
until the moisture is driven off and a layer of caoutchouc left 
on the bat. The thickness of the layer is repeatedly in- 
creased by alternately dipping the bat into the juice and 
then drying it. When the layer has reached the desirable 
thickness it is split up one side and removed from the form 
and hung up to be further dried. There are several other 
methods of preparing the caoutchouc from the milky juice, 
the object in each case being to get rid of the liquid in which 
the caoutchouc is suspended. The manner in which the 
caoutchouc is dried and the source from which it is obtained 
account for the different forms that come into market. 

All raw caoutchouc contains albuminoid and resinous 
bodies and often mechanical impurities, as woody fibre, 
earthy matter, etc., from which it must be freed before it can 



280 

be used for manufacturing purposes. The mechanical treat- 
ment of the caoutchouc is interesting and varies with the 
object to "which it is to be put but it cannot be described 
here. The best caoutchouc comes from the province of Para 
in Brazil and other provinces of that country. It also comes 
from Central America. Africa, Madagascar. Asia and some 
of the East India Islands. 

Caoutchouc is almost equally valuable for its physical and 
chemical properties. Its lightness, elasticity, and imper- 
meability to water are among its most valuable properties. 
Caoutchouc is insoluble in alcohol but slowly dissolves in 
carbon disulphide, naphtha, petroleum spirit, turpentine, 
and benzene — the last two being the best solvents, but the 
petroleum solvents are generally equally used because of 
cheapness. Caoutchouc is not acted upon by the alkalies or 
the dilute acids. It is slowly oxidized in moist ah"-. It 
hardens and loses its elasticity by cold and softens and 
becomes sticky by heat. At about 12u : C. it melts and 
decomposes into a black viscous mass which does not harden 
and is a valuable lubricant for air-tight stoppers. 

Vulcanized Rubber. When caoutchouc is mixed with a 
small per cent of sulphur and the mixture heated to about 
150 c C. it undergoes a most beneficial change and is said to 
be vulcanized. It is thought that some of the hydrogen of 
the caoutchouc is replaced by the sulphur and a sulpho- 
compound produced. The vulcanization of the rubber is 
accomplished after the rubber is mechanically purified. For 
this purpose about ten per cent by weight of sulphur is 
thoroughly incorporated with the rubber and the mixture 
subjected to the necessary temperature. Only a fraction of 
the entire sulphur seems to combine with the rubber but the 
presence of the remainder is necessary to secure the effect. 
The vulcanization by heat is always accomplished after the 
rubber articles are made into required form. Such articles 
are molded into shape or the different parts cut out and 



281 

joined together by rubber cement after the sulphur has been- 
incorporated with the rubber. 

Certain other bodies besides sulphur are often added to 
the rubber. These are not known to act otherwise than 
mechanically but seem to be beneficial; they are such as 
zinc, lead, and iron oxides, steatite, calcium and lead car- 
bonates. 

Water-proof cloths are made by spreading* the sulphurred 
rubber in a plastic state by machinery upon the surface of 
the fabric. Two pieces of cloth may be made to pass through 
rollers with their "spread-sides" toward each other which 
produces water proofing of double texture. The film of 
rubber spread upon the cloth may be made of any desired 
thickness. Water-proof cloths may be vulcanized by sub- 
jecting them to the required temperature or by what is 
known as the cold process. In this process the spread cloth 
is drawn slowly through a solution of sulphur chloride in 
carbon disulphide during which the thin rubber sheet takes 
up the required sulphur and need not be subsequently 
heated. The cold process is not as efficient as that first 
described. 

The effects of vulcanization are to greatly increase the 
elasticity of the rubber and to prevent its cohering under 
pressure and adhering to other bodies when warm. It is no 
longer affected by cold, its porosity is diminished, and it is 
no longer soluble in the solvents of common rubber. 

The water-proofing of fabrics by solution of rubber was 
patented by Mackintosh in 1824. Certain garments are still 
named from the inventor. The vulcanization of rubber was 
discovered by Goodyear in 1843. 

Vulcanite. With a greater proportion of sulphur (twenty 
to thirty-five per cent) and a still higher temperature the 
rubber is converted into vulcanite or ebonite. It is much 
harder and more rigid than rubber and is used in the manu- 
facture of combs, rulers, discs, etc. 



282 

Rubber Tubing and Threads. Knbber tubes are made in 
two ways — 1st, the rubber is brought to a semi-plastic condi- 
tion and forced through an annular mould or die, consisting 
of two concentric cylinders with the necessary space between 
them. 2nd, By cutting rubber bands of the proper width 
and joining their freshly cut edges by pressure, the bands 
being wrapped around a mandrel of the proper size. 

Rubber threads are either cut from the sheets or the semi- 
liquid rubber is pressed through sieve-like moulds. The first 
method gives the rectangular threads, the latter the round. 

Gutta-percha. This substance has the same empirical 
formula as caoutchouc. It is like that substance obtained 
from exudation of certain trees. It comes mainly from the 
Islands of the Indian Archipelago — its name signifies the 
gum of the percha tree. The crude gum is procured in 
the same way as caoutchouc and it is subjected to about the 
same mechanical process to free it from impurities. It is 
harder and less elastic than caoutchouc. It is not attacked 
by alkalies or dilute acids but is acted upon by strong nitric 
or sulphuric acid. It is an excellent electric insulator and is 
extensively used as a casing in submarine telegraphy, and 
for the covering of electric wires. It is largely used in the 
manufacture of medical instruments and for many cheap 
ornaments. 

Gutta-percha was for a long time obtained by felling the 
trees, the juice then exuding from incisions made at many 
places along the body and branches. This injudicious 
method was beginning to imperil the supply and has now 
been stopped. Because of the great demand for gutta- 
percha and caoutchouc, the English Government has at- 
tempted to cause the artificial production and spread of the 
parent trees. 

ALCOHOLS. 

This term is applied to a large number of bodies which in many 
respects differ widely from each other, but may all be considered as oxy- 
gen derivatives from the hydrocarbons. The relations of the alcohols 



283 

indicate that they may be considered as derived from the correspond- 
ing- hydrocarbons by the substitution of hydroxyl (OH) for an atom of 
hydrogen. Thus methyl-alcohol has the composition CH 3 ,OH which 
may be supposed to result by substituting (OH) for H in CH 4 ; propyl- 
alcohol has the composition C 3 H 5 (OH) 3 which results by substituting 
(0H) 3 for H 3 in propane, C 3 H 8 . It is evident therefore that they may 
be considered as compounds of hydroxyl and hydrocarbon radicals of 
different degrees of valency. 

Alcohols are said to be monatomic, diatomic, triatomic, etc., or 
monohydric, dihydric, trihydric, etc., according to the number of 
hydroxyl groups they contain. Each series of hydrocarbons has its 
derived alcohols. It will be necessary to refer to only a few of this 
large class of bodies. 

Alcohols of the Paraffin Series. The alcohols of this series are the 
most important of these bodies and embrace all of those that need to 
be referred to here. They may be considered as derived from the paraf- 
fin hydrocarbons by the substitution of (OH) for H. 

Monohydric Alcohols. The lowest members of the series of alcohols 
are mobile liquids, the middle members are oily liquids, and those con- 
taining twelve or more carbon atoms are solids. 

There are two very important monohydric alcohols, the methyl- 
alcohol and the ethyl-alcohol, their formula? beingCH 3 OHandC 2 H 5 OH, 
the corresponding paraffins are methane (CH 4 ) and ethane (C 2 H 6 ). 

Methyl-Alcohol; CH 3 (GH). This body is popularly known 
as wood-spirit and is found among' the products which result 
from the destructive distillation of wood. The condensed 
products from distilled wood separate into lighter and heavier 
parts. The lighter part is the crude wood- vinegar and con- 
sists mainly of an aqueous solution of acetic or pyroligneous 
acid with a small proportion of methyl-alcohol. By fractional 
distillation the alcohol can be separated and purified. In the 
impure state after one distillation it is sold as wood-naphtha. 
Large quantities of methyl-alcohol are now made by distil- 
ling certain residues which result in the beet-root sugar fac- 
tories after the fermentation of the molasses for the produc- 
tion of common alcohol. 

Pure methyl-alcohol is very similar in smell, taste, and 
appearance to common alcohol. It dissolves resins and 
volatile oils, can be burned in lamps, and for all these pur- 



284 

poses can be used as a substitute for common alcohol. 
When crude it has an offensive odor and a very disagreeable 
taste. 

Ethyl- Alcohol, Common Alcohol. This is the longest and 
best known of the alcohols and is generally designated sim- 
ply by the term alcohol. It is a monohydric alcohol derived 
from the second member of the paraffin series, ethane (C 2 H 6 ), 
by the hydroxyl substitution C 2 H 5 ,OH. 

Alcohol can be made artificially by the synthesis of its 
elements, C 2 H 2 being first produced, this converted into C 2 H 4 , 
and then converted into alcohol. 

Alcohol for commercial purposes is always obtained from 
the fermented products of certain kinds of sugar. Fermenta- 
tion is a slow process of transformation which is brought 
about in certain organic bodies by means of substances called 
"ferments." All ferments are unstable nitrogenous bodies 
and may be divided into two classes. 1st, Those having an 
organized structure and capable of growth and multiplica- 
tion; 2d, Those without structure and incapable of repro- 
duction. 

The alcoholic or vinous fermentation, by which alcohol is 
produced from sugar, is brought about by a ferment of the 
first class called yeast, which is a vegetable micro-organism. 

If to a solution of grape or cane sugar (which contains in 
addition the necessary elements for the growth of the yeast) 
a little yeast be added the process of fermentation will be set 
up, during which the sugar will be converted into carbon 
dioxide and alcohol. The precise action of the yeast is not 
known but it is during the growth of the yeast that the 
change is brought about. In the case of grape sugar or 
glucose (CeH^Oe) the molecule seems to split into carbon 
dioxide and alcohol, C 6 Hi 2 6 =2C 2 II 6 0+2C0 2 . Cane sugar 
(Ci 2 H 22 0n) is first converted by the yeast into glucose by the 
assumption of a molecule of water, Ci 2 H 22 Oii+H 2 0=2C 6 Hi 2 6 ; 
the glucose is then resolved as before. 



285 

Note. — During- the fermentation other substances are produced the 
most important of which are glycerine, succinic acid, and fusel oil, 
but about 95 per cent of the sugar may be converted into alcohol and 
carbon dioxide. 

Fermentation does not take place at a temperature below 
32° F. nor above 95° F. Many chemicals arrest and prevent 
fermentation, such as the strong acids and antiseptics. 

Pure yeast spores will not ferment a pure solution of 
sugar because the constituents for the growth of the yeast 
are absent. Water containing more than one-half its weight 
of sugar in solution can not be fermented by yeast and the 
fermentation ceases when the alcohol produced constitutes 
one-sixth the weight of the solution. The yeast increases 
greatly in weight when the necessary food constituents are 
present. 

The sugars most generally fermented for the production 
of alcohol are not those from the cane and grape but those 
from the starch of grain and potatoes. The starch (C 6 Hio0 5 ) is 
first converted into glucose (C 6 Hi 2 6 ) by the action of dilute 
acid or into maltose (C12H22O11+OH2) by the process of malt- 
ing yet to be described. 

The maltose undergoes the vinous fermentation under the 
action of yeast just as do the other sugars mentioned. 

By successive fractional distillations of the fermented 
solutions pure alcohol is obtained. 

Pure alcohol is a colorless mobile liquid, has a pungent 
odor and a piercing, burning taste. Its boiling point is below 
that of water (78° C.) and it freezes at— 130° C. It burns with 
a pale blue flame free from smoke. It mixes with water in 
all proportions and has considerable affinity for it, absorbing 
its vapor from the air and abstracting it from animal and 
vegetable substances immersed in it. This fact partly ex- 
plains its action in preserving bodies. Its dilution with 
water results in contraction of volume and a considerable 
rise of temperature. 

Alcohol is very valuable in the laboratory as a solvent 



286 

standing next to water in this respect. It dissolves a large 
number of both organic and inorganic compounds and is 
especially useful in dissolving the resins, essential oils, etc. 

The strength of alcohol can be determined from its 
specific gravity and tables are prepared for this purpose. 
Absolute alcohol has a specific gravity of .79 at 15° C. Its 
strength decreases as its specific gravity increases. So-called 
proof-spirit has a specific gravity of .92 and contains 49 parts 
by weight of alcohol. If the alcoholic solution contains 
other bodies than water the specific gravity, of course, does 
not indicate the strength. 

It may be observed that ethyl-alcohol is a homologue of 

methyl-alcohol as appears from their formulas, CH 3 ,OH and 

C 2 H 5 ,OH, the two differing by CH 2 . 

The acetylene, olefine, and benzene series of hydro-carbons have 
their mono-hydric alcohols which may be regarded as formed from 
these hydrocarbons in the same manner as the ordinary alcohols are 
formed from the paraffin series. 

GLYCEKOLS; TEIHYDEIC ALCOHOLS. 

These alcohols may be considered as derived from the 
paraffin hydrocarbons by the replacement of three hydrogen 
atoms by three molecules of (OH). Only a few such are 
known. The most important of these only will be referred to. 

Glycerine; Propenyl or Propyl Alcohol. The basic mem- 
ber of the paraffin series for this alcohol is propane (C 3 H 8 ) in 
which three atoms of hydrogen have been replaced by three 
molecules of (OH). 

Preparation of Glycerine. It has already been stated 
that glycerine is produced during vinous fermentation, but it 
is always prepared by saponifying the natural fats. 

The natural fats are ethereal salts of the fatty, organic 
acids, that is, salts of the organic acids in which the typical 
hydrogen of the acid is replaced by the alcohol radical. The 
more important of the animal and vegetable fats and oils are 



287 

mainly composed of a fatty acid in which the hydrogen is 
replaced by the radical of propenyl-alcohol or glycerine 
(C3H5). Such fats are therefore termed glycerides and rep- 
resenting the fatty acid by HFt the formula for the fat or 
ethereal salt will be C 3 H 5 Ft 3 . 

When these fats are boiled with a caustic alkali there is 
produced a soap and an alcohol and the process is termed 
saponification. The reaction may be indicated thus, C 2 H 5 Ft 3 + 
3KOH=C 3 H 5 (OH) 3 +3KFt, 

The potassium salt of the organic acid is a common soap. 
The term saponification is not now limited to the actual pro- 
duction of a soap but includes as well the processes by which 
ethereal compounds are resolved into an alcohol and a fatty 
acid. 

Pr^apa4io»-©i^€J'lyeeFitte». Glycerine is now produced by 
the action of super-heated steam upon fats, saponification by 
super-heated steam. The action of the steam is similar to 
that of the alkali and may be represented by the reaction 
C 3 H 5 Ft 3 (fat) +3H 2 = C 3 H 5 (OH) 3 +3HFt. The chemical re- 
sults of saponification are expressed in the above reactions 
and the subsequent preparation of glycerine is a question of 
purification. When pure fats or oils are saponified by steam 
the glycerine and the fatty acid are both obtained pure. 
Crude glycerine is obtained in large quantities in the prepa- 
ration of soap and of the fatty acids. Glycerine has been 
prepared artificially. 

Properties of Glycerine. Pure glycerine is a colorless 

viscid liquid without odor and it has a very sweet taste. It 
readily absorbs moisture and mixes with water in all propor- 
tions. Its boiling point is about 290° C. and it solidities a1 
about 40° C. It burns with a bluish flame when heated to 
150° C. At high temperature it volatilizes and partially 
decomposes yielding acrolein (C 3 H 4 0), which gives the dis- 



288 

agreeable odor often observed from a partially extinguished 
candle. 

Grlycerine is a very powerful solvent, dissolving many 
substances more freely and some that water will not dissolve. 
It ranks next to water as a solvent. Grlycerine is sometimes 
used in confectionery to sweeten and by brewers to increase 
frothing in beer. Because of its attraction for water it is 
used to prevent certain bodies from becoming dry and hard, 
such bodies being moist with it, as sponges when used for 
cushions or mattresses. Its most important use is in the 
manufacture of nitro-glycerine and other high explosives yet 
to be described. 

By a comparison of the formulae of the three alcohols described, it 
will be seen that they constitute an homologous series of which methyl- 
alcohol is the first term. These formula? will also show that ethyl- 
and propyl-alcohol may be considered as derived from the methyl-alco- 

atom of 



etc. 



The series might be continued to include other members of the mono- 
hydric alcohols. It will be seen by considering the formula? that the 
different alcohols appear to be derived from methyl-alcohol by the sub- 
stitution of hydrocarbon groups for an atom of hydrogen. An alcohol 
from methyl by the replacement of only one atom of hydrogen by a 
hydrocarbon group is a primary alcohol ; all of the above are primary 
alcohols. If two atoms of hydrogen in methyl alcohol are replaced by 
hydrogen radicals the result is a secondary alcohol and if three be thus 
replaced it is a tertiary alcohol. The general formula? for primary, 
secondary and tertiary alcohols would be represented as below in 
which R stands for a hydrocarbon radical. 

f R ( R f R 

( 1 H C ] H ° 1 R 

[OH [OH [OH 

Primary alcohol, Secondary alcohol, Tertiary alcohol. 

The formula? representing the constitution of the alcohols are the 
results of generalizing from many experimental facts and they serve 
admirably to explain the facts. 



d1 by the 


substituti 


on 


of a hydrocarbon radical for an 


°] H 
[OH 






( CH 3 ( CH 5 
[OH I OH 


Methyl alcohol, 


Ethyl alcohol, Propyl alcohol 



289 

The oxidation of primary alcohols by which hydrogen is removed 
and no other (mange in the atomic constitution produced yields an 
aldehyde. The aldehydes from primary alcohols differ in constitution 
from the parent alcohol by two atoms of hydrogen — thus ethyl alcohol 
by losing two atoms of hydrogen yields acetic aldehyde (C 2 H 4 G). The 
other primary alcohols yield corresponding aldehydes. The similar 
oxidation of the secondary alcohols with the elimination of hydrogen 
yields the ketones or acetones, which are the aldehydes of the secondary 
alcohols. 

ACETIC ACID. 

This acid is a member of a group of organic acids which may be 
considered derivatives by oxidation of the primary alcohols or from the 
aldehydes of these alcohols. They are generally called fatty acids 
because many of them are contained in fats or derived from them. 

Preparation of Acetic Acid. Acetic acid occurs among 
the products of the destructive distillation of wood and much 
acid is obtained from this source. The crude acid from 
wood is called pyroligneous acid and is found in the aqueous 
or lighter of the two layers into which the condensable 
products of the wood separate. The acetic acid is generally 
obtained from the solution by first producing an acetate by 
the addition of a suitable base and then decomposing the 
acetate by a less volatile acid. The acid liquor is generally 
neutralized by sodium carbonate and concentrated to crystal- 
lization by evaporation. The sodium acetate is carefully 
heated to expel tarry matter and distilled with sulphuric or 
hydrochloric acid, NaC 2 H 3 2 +H 2 S0 4 =C 2 H i 2 +NaHSO,. Dur- 
ing this operation the acetic acid passes over and is collected. 
An impure acetic acid may be prepared by carefully dis- 
tilling the crude liquid without previous neutralization. 

Alcohol may be oxidized to acetic acid by means of 
platinum black in a very short time. Some chemical works 
especially on the continent of Europe have employed this 
method. The power of the platinum to accomplish this 
oxidation is undoubtedly due to its power of condensing 
gases already referred to. The alcohol is placed in evaporat- 
ing dishes in each of which stands a small tripod a couple of 
19 



290 

inches high. The tripod supports a smaller dish or watch- 
glass in which the platinum black is contained. By a 
suitable temperature the alcohol is volatilized and the vapor 
oxidized by the oxygen condensed on the platinum. The 
operation is accomplished in a suitable case or chamber to 
which the air has to be admitted at proper intervals. The 
pure acid is prepared by distilling the pure sodium acetate 
with pure sulphuric acid. 

The pure acid is a clear colorless liquid and has a pleasant 
but penetrating odor. It has a very sharp acid taste and 
when pure blisters the skin. The boiling point is 118° C. and 
below 170 : C. it is generally solid giving glacial acetic acid. 
Its vapor burns with a pale blue name. Most of its salts are 
soluble, hence it can not be readily precipitated. 

Acetic acid is largely used in the dilute form as vinegar 
and in the preparation of various acetates many of which are 
used in the arts. The acid is an important solvent for many 
organic bodies and is accordingly valuable in the laboratory. 

Preparation of Vinegar. Acetic acid is the acidifying 
principle of common vinegar. Vinegar is always made by 
the oxidation of alcohol and the best vinegar is made by the 
spontaneous acidification of wine or cider. It is only necessary 
to expose the wine or cider to the action of the air at a suit- 
able temperature. The alcohol present in the liquor is 
gradually converted into acetic acid by oxidation, C 2 H 6 0+ 
O^CoILO-^HoO. The oxidation in this case is known to be 
brought about by a microscopic vegetable organism, mij co- 
derma aceti, in the fermented liquor. The wine or cider 
contains the necessary ingredients' for the growth of the 
organism and the oxidation of the alcohol is in some way 
brought about by the plant. Fermented liquors are very 
liable to become sour owing to this action but distilled liquors 
are not subject to the change since the food constituents for 
the organism do not exist in them. 

Vinegar is also made by mixing dilute alcohol or other 



291 

distilled spirits with yeast or other nitrogenous organic mat- 
ter and exposing it to the air. The added matter contains 
the constituents of growth necessary for the ferment and the 
action is the same as for fermented liquors. The conversion 
of the alcohol into the acetic acid may be hastened by per- 
fecting the exposure of the spirituous liquors to the air. The 
quick vinegar process consists in causing the wine or other 
prepared alcoholic liquor to trickle through casks containing 
shavings so as to expose a large surface to the air, the shav- 
ings having been steeped in vinegar to assure the presence of 
the ferment. 

Vinegar contains usually not over 5 per cent of acetic 
acid. In some countries it is permitted to add one-tenth of 
one per cent of sulphuric acid to the vinegar to prevent 
further mothering. 

In this country a large quantity of excellent vinegar is 
made by the farmers from cider. 

ACETATES. 

Acetic acid is a monobasic acid and forms a large 
number of salts. Many of these acetates are employed in 
the arts and some of the more important will be mentioned ; 
all of the normal acetates are soluble. 

Aluminum Acetate. This salt is prepared by bringing 
together in solution common alum (double sulphate of 
aluminum and potassium) and lead acetate. Lead sulphate 
is precipitated and separated by filtration. The solution of 
aluminum acetate is largely used in dyeing and calico print- 
ing. The cloth is impregnated with a solution of the salt 
and subjected to a moderate heat or other process of "fixing" 
by which it is converted into an insoluble basic acetate in 
the fibre of the cloth. The fibre is then capable of taking up 
and setting permanently the coloring matter. Such bodies 
are called mordants and the acetates of the sesquioxides or 
weaker bases are the most useful, for they are most easily 



292 

converted into insoluble basic salts. The sesquioxides of 
aluminum and chromium form very important acetates. The 
solution of aluminum acetate is generally termed red liquor in 
the factories owing to the fact that it is so generally employed 
in fixing red colors. The red liquor may be prepared from 
aluminum sulphate instead of alum. 

Lead Acetate. This compound is prepared by dissolving 
litharge in acetic acid or by acting upon sheet lead with the 
vapor of acetic acid. It can be obtained in distinct crystals 
but is usually indistinctly crystalline. It has a sweet taste 
and is frequently called "sugar of lead." It is very exten- 
sively used in the preparation of alum mordants and in the 
manufacture of certain pigments. It is a valuable article in 
the laboratory. 

Copper Acetates. Verdigris is a mixture of several basic 
copper acetates and results when copper is simultaneously 
exposed to the action of the air and the vapor of acetic acid. 
It finds some use in oil and water colors, in calico printing 
and in the preparation of certain paints. 

Sodium Acetate. Is prepared by the action of acetic 
acid upon sodium carbonate. The solubility of the acetate 
in water increases very rapidly with the increase of tempera- 
ture and the supersaturated solutions have been used in foot- 
warmers in certain European railways. The cooling of the 
heated solution is greatly retarded by the heat given out by 
the crystallization of the salt. 

SOME IMPORTANT VEGETABLE ACIDS. 

Four of the more common vegetable acids are oxalic, tartaric, 
malic, and citric — they are all paraffin derivatives. 

Oxalic Acid. This acid occurs free in certain varieties of boletus 
(pink or touchwood mushroom), combined with potassium in sorrel 
and certain plants of the rumex (dock) species and in garden rhubarb 
and as calcium salts in many plants. 

Oxalic acid is produced on the manufacturing scale by the oxida- 
tion of highly carbonized organic bodies such as starch, sugar, and 



2m 

cellulose. The principal commercial process now is by the oxidation 
of sawdust. 

The acid can be obtained in colorless transparent crystals which 
are soluble in less than their own weight of hot water and in about 
eight parts of water at 15.5° C. The solution has a very sour taste 
and is very poisonous. Chalk or magnesia furnishes the best antidote. 

The acid is largely used as a discharge in calico printing and dyeing, 
for bleaching flax and straw, for removing ink and iron stains from 
linen, and for cleaning metals, marble, and wood. 

Oxalic acid is bibasic (CaH^O^) and its metallic salts are in general 
soluble, that of calcium being least so. Calcium chloride maybe used as 
test for a soluble oxalate. 

Tartaric Acid; C 4 H 6 O e . This term and formula include four 
isomeric bodies but they differ in physical properties. The ordinary 
tartaric acid is the acid of tamarinds, mulberries, pine-apples, grapes, 
and several other fruits. It occurs in the pure state in small quantity 
but is usually present in combination with potassium as an acid salt. 
The commercial supply of the acid is obtained from grape juice. 

During the fermentation of grape juice in the manufacture of wine 
an impure acid potassium tartrate is deposited, which is known as 
argol or cream of tartar. This tartrate is dissolved and neutralized by 
the addition of powdered chalk or lime by which calcium tartrate is 
precipitated. The calcium tartrate is heated with sulphuric acid when 
calcium sulphate is formed and the tartaric acid left in solution, which 
can then be crystallized by evaporation. 

Tartaric is one of the most important vegetable acids. It is largely 
used in the printing industries both as a "resist" and as a "discharge" 
and also as a mordant in dyeing wool. It is remarkable as forming a 
very slightly soluble acid potassium tartrate when a potassium salt in 
solution is added to a solution of the acid, thus serving as a prelimi- 
nary test for a potassium salt in solution. 

Tartaric acid forms a large number of single and double salts. 
Rochelle salt is a double tartrate of potassium and sodium. Tartar 
emetic is a double tartrate of potassium and antimony. Tartaric acid 
is bibasic. 

Malic Acid. This acid or its salts are widely distributed in the vege- 
table kingdom. The acid occurs in grapes, unripe apples, blackberries. 
and in considerable quantity in the garden rhubarb. It is generally 
prepared from the unripe berries of the mountain ash. 

Malic acid is bibasic and its formula is C 4 H e 5 . 

Citric Acid. Citric acid occurs in large quantity in the juice of 
lemons, limes, bergamots, and is present in many other fruits and in the 
sap of many plants. It is prepared in the largest quantity from Lemon 
juice. This juice is neutralized by chalk and the calcium citrate pro- 



294 

duced is decomposed by sulphuric acid. The uses of the acid are well 
known. Some of the citrates as those of iron and magnesium are used 
in medicine. 

The acid is tribasic, its formula being C e H 8 7 . 

Tannic Acid, Tannin. This name has been given to a group of plant 
constituents which are capable of precipitating a solution of gelatine 
and of uniting with animal membrane giving a more or less perfect 
leather. 

Gallotcumic Acid. This is the best known and most important of 
this group and is generally called tannic acid. It is present in large 
quantity in gall-nuts from which it may be obtained by digesting the 
powdered gall-nuts in an aqueous solution of ether. Upon filtering the 
solution and allowing it to stand, the ether separates from the water 
carrying with it the coloring matter, the water containing the acid. 
By evaporation the gallotannic acid is left as a yellowish, friable, amor- 
phous mass showing no tendency to crystallize. A strong solution of 
gallotannic acid gives a precipitate when mixed with sulphuric or 
hydrochloric acid. The acid precipitates albumin and gelatine. 

With ferric salts the acid gives a blue-black precipitate which is the 
basis of certain writing inks. A tincture of nut-galls is accordingly a 
delicate test for the presence of ferric salts. 

The tannins, extracted from the oak. hemlock and similar species 
and which are used for tanning leather are closely related to the gallo- 
tannic acid and are employed in tanning because of their similar action 
on gelatine. 

ALCOHOL ETHERS. 

This class of ethers may be considered as derived from 
the alcohols by replacing" the hydrogen in the hydroxyl of 
the alcohol by an alcoholic radical. Thns in ethyl alcohol 
C 2 H 5 ,OH, if the hydrogen of the hydroxyl be replaced by the 
ethyl alcohol radical (C 2 H 5 ), we shall have C 2 H 5 OC 2 H 5 . 

We may also consider them as oxides of the alcohol 

TT- 
radicals p 2 TT 5 0, or as anhydrides of the alcohols formed by 

the elimination of the water from two molecnles of alcohol, 
2C 2 H 6 0— H 2 O = GH 10 O. 

Ethyl-ether, Common Ether. This compound can be pro- 
duced by the action of several dehydrating- agents upon alco- 
hol but the process is not one of simple dehydration. Ether 
is made on a large scale by distilling a mixture of alcohol 



295 

and sulphuric acid. The first action when the alcohol and 
acid are heated together results in the formation of ethyl- 
sulphuric acid, H 2 S0 4 +C 2 H 5 OH=C 2 H 5 H80 4 +H 2 0. When 
the ethyl-sulphuric acid is heated with more alcohol, ether 
results and the sulphuric acid is reproduced, C 2 H 5 HS0 4 + 
C 2 H 5 OH=C 4 H 10 O-fH 2 SO 4 . 

This acid will act upon fresh alcohol and if the supply of 
alcohol be properly regulated and the temperature kept 
within proper limits the etherification process can be made 
continuous. 

The continuous operation is effected by distilling the mix- 
ture of acid and alcohol in a retort so arranged as to admit 
fresh alcohol in regulated quantity so that the temperature of 
the mixture is kept within the required limits, about 140° C. 

The ether and water distil over and are condensed in a 
receiver together with some alcohol and a little sulphurous 
acid. The sulphuric acid is gradually used up so that the 
process can not be continued indefinitely with the same 
supply of acid. 

To avoid the danger of contact of the alcohol vapor with 
flame, coils of tubing conveying superheated steam or the 
vapor of some liquid of high boiling point are used as the 
source of heat. The distillate is shaken with water which 
removes most of the alcohol, a base (lime, potash or soda) is 
added to fix the sulphurous acid. The remaining water is 
removed by distilling over lime or calcium chloride. These 
operations may be partially repeated for greater purity. 

Properties of Ether. Ether when pure is a thin, mobile, 
transparent and colorless liquid with fragrant odor and 
peculiar taste. Its specific gravity at 15° C. is .70. Its boil- 
ing point in the air is 34.9° C. Under atmospheric pressure 
it evaporates rapidly producing great cold. It is very com- 
bustible and its vapor very dense, which properties make 
careful handling necessary for safety. It mixes with alcohol 
in all proportions but is slightly soluble in water (one part 



296 

in ten). This fact gives a means of separating- it from 
alcohol when the latter is not present in too large a qnantity. 
Ether is a solvent for resins, fats, alkaloids, and many 
other organic substances. It also dissolves phosphorus, 
iodine, and bromine. It is used to dissolve collodion cotton 
in photography and as an anaesthetic. 

CYANOGEN AND ITS COMPOUNDS. 

Cyanogen (C 2 N 2 ),is a colorless gas with the odor of bitter almonds. 
It is very poisonous. Cyanogen occurs in the gases of blast furnaces 
and can be prepared by heating silver cyanide strongly (AgCN). Silver 
cyanide is produced when potassium cyanide and silver nitrate are 
brought together in solution, KCN+AgN0 3 =KN0 3 +AgCN. Potassium 
cyanide is always produced when nitrogen, charcoal, and potassium 
carbonate are highly heated together. Cyanogen is generally obtained 
by heating mercuric cyanide. In many compounds, cyanogen acts like 
an element. It may be regarded as a monovalent group and is gener- 
ally represented by Cy. 

Hydrocyanic Acid; HCN. This acid commonly known as prussic 
acid is found in the kernel of the peach and plum stones and in the 
leaves of the cherry and the laurel. It can be prepared by acting upon 
metallic cyanides with hydrochloric acid, KCN+HC1=KC1+HCN. It is 
a colorless liquid and very volatile. The inhalation of the vapor is 
very dangerous and the acid taken internally is one of the most fearful 
poisons known. 

Potassium Ferrocyanide. Yellow prussiate of potash, (KCN) 4 , 
Fe(CN) 2 ,Aq., double cyanide of potassium and iron. This salt is the 
source of most of the cyanogen compound's and is made on the large 
scale by melting together potassium carbonate and iron filings or 
scraps, mixed with organic matter containing carbon and nitrogen. It 
crystallizes in large, lemon-colored crystals, readily soluble in water. 
This ferrocyanide is a chemical reagent of great importance and value, 
with a large number of metallic salts it gives precipitates which are 
frequently very characteristic. It is largely employed in the manufac- 
ture of colors, in dyeing and calico printing, and as stated, is the 
source of many of the compounds of cyanogen. 

Potassium Cyanide ; KCN, KCy. This substance as already stated, 
is produced when nitrogen is heated to a high temperature in contact 
with potassium carbonate and charcoal. It is also produced when 
potassium is heated in cyanogen gas or the vapor of hydrocyanic acid 
but it is generally prepared by fusing the ferrocyanide of potassium 
with potassium carbonate. The cyanide then generally contains some 
cyanate and carbonate of potassium, but for most applications this 
impurity is not important. 



297 

A solution of KCy dissolves the chloride and iodide of silver, in con- 
sequence of which it finds use in photography. It is used in the extrac- 
tion of gold from its ores and its double cyanide with gold and silver 
are used in electroplating and gilding. Its great solvent powers make 
it useful in cleaning gold and silver. 

Potassium Ferricyanide ; (KCN) 3 , Fe(CN) 3 . This salt is often termed 
the red prussiate of potash. It is prepared by the oxidation of the yel- 
low T prussiate of potash. It is a powerful oxidizing agent when used 
with alkali; such a preparation bleaches indigo. It is used in calico 
printing. 

Mercuric Cyanide; Hg(Cy) 2 . This cyanide is prepared by dissolving 
mercuric oxide in hydrocyanic acid. It is used to obtain cyanogen. 

There is a large number of other cyanides, the most important of 
which are certain complex cyanides used as colors. Such are Prussian 
Blue, a complex cyanide of iron ; Hatchets Brown, a cyanide of iron 
and copper. 

PHENOLS. 

The phenols are benzene derivatives in which hydrogen 
of the benzene group is replaced by hydroxyl. They are 
derived from the benzene hydrocarbons in the same way 
that the alcohols of the fatty series are derived from the 
paraffins. 

Phenol, Hydrobenzene, Carbolic acid, Phenic acid, C 6 H 5 OH. 
Phenol is found among* the products resulting from the de- 
structive distillation of wood and coal. It is usually pre- 
pared from coal tar, being the chief constituent of the acid 
portion of this tar. It is concentrated by collecting apart 
that portion of the heavy oil from coal tar which distils over 
between 150° and 200° C. It is extracted from the distillate. 

•Phenol crystallizes in colorless needles which have the 
odor of coal tar. It liquefies at 42° C. and is then slightly 
heavier than water. It is soluble in 15 parts of water at 
common temperature. It is poisonous, blisters the skin and 
exerts an antiseptic action, arresting fermentation and putre- 
faction. There are several disinfecting powders which con- 
sist of carbolic acid mixed with mineral matter. 



298 

CARBOHYDRATES. 

This term includes three groups of bodies each of which 
contains six atoms of carbon or some multiple of six and 
oxygen and hydrogen in the proportion to form water. These 
groups are nearly allied to each other and widely distributed 
in nature. 

The three groups are the glucoses, the sucroses or saclia- 
rides, and the amy loses. The first two groups constitute the 
sugars, the last includes the starches and the celluloses. The 
formula of the glucoses is CeH^Oe; of the sucroses G2H22O11 
and of the amyloses (C 6 Hi O 5 )n. 

The first two groups are among the most important foods 
of the civilized nations and the last supplies man with a large 
portion of both food and clothing. 

Some bodies are now classed as among the carbohydrates which do 
not contain six atoms of carbon. The general formula of the glucoses 
is C n (H 2 0)n but n is not always six; of the sucroses C n (H 2 0) n -i; of the 
amyloses (C 6 H 10 5 ) n . Several of the sugars have been shown to be 
aldehyde or key tone alcohols. 

Glucoses. Ordinary glucose; Dextrose C 6 Hi 2 6 . Ordinary 
glucose is the most important member of the glucoses. It 
exists in the juice of sweet grapes, in raisins, and in honey 
of which it forms the crystalline portion. Its presence in 
urine is characteristic of the disease called diabetes. 

Dextrose is made on a commercial scale from starch by 
heating it with dilute sulphuric acid. In this country it is 
made in enormous quantities from corn-starch, hence, is some- 
times called corn-sugar. The starch is obtained from maize 
or Indian corn and will be referred to under the subject of 
starch. In other countries starch from other sources is used. 

In this country the term glucose among the manufacturers 
is limited to the liquid products and such use of the term has 
become very general. The solid product is termed sugar. 
The manufacture of glucose in the United States is an 
immense industry and the products in both the solid and 



299 

liquid forms are very extensively used ; many kinds of syrup 
are composed of the liquid glucose and the solid is largely 
used in confectionery and as sugar. 

The conversion of the starch is accomplished by boiling 
it with water in large converters with from one to one and 
one-half per cent of sulphuric acid. The heating is often 
done in closed converters and under considerable pressure, 
steam being admitted for the purpose. The higher the pres- 
sure the shorter the time required for the conversion. For 
the liquid glucose less acid and less heating are required than 
for the sugars. During the heating the starch first passes 
into the isomeric dextrin and this takes up the elements of 
water to form dextrose, (CeHioO.^n+f^O^^CeH^OeK. 

The acid is removed by the addition of powdered chalk 
and the liquid filtered through animal charcoal and evapo- 
rated to the desired consistency. The evaporation is fre- 
quently done in vacuum pans. The glucose can be made 
perfectly colorless. A little cane syrup is often added to the 
glucose to give the desired color. Some glucose is employed 
in the preparation of artificial honey, the comb being made 
of paraffin. 

Liquid glucose obtained as above described contains con- 
siderable dextrin and maltose with some organic salts of 
calcium. The first two substances are less abundant in the 
solid glucose. Chemically pure glucose has to be obtained 
through further treatment. 

Dextrose is less sweet and the solid forms less soluble 
than cane sugar. 

The cellulose of wood fibre can be converted into glucose 
and some of the wood-paper manufacturers have attempted 
the commercial manufacture of glucose from this source. 

Fruit Sugar; Laevulose; C e H 12 6 . Fruit sugar nearly always ac- 
companies dextrose in the juice of sweet fruits. Is is more difficult to 
crystallize than dextrose. It is sweeter than dextrose and Less easy to 
ferment. A mixture of dextrose and lsevulose in equal proportions 
constitutes "invert" sugar. 



300 
SUCBOSES. 

Common Sucrose; Cane Sugar; Ci 2 H L >di. Cane sugar is 
the most important member of this group. It is very widely 
distributed in the vegetable kingdom but is obtained on a 
commercial scale from only a few plants. The principal of 
these are the beet-root, sugar cane, sorghum, sugar maple, 
and a species of palm. A small amount is made in this 
country from the ash-leaved maple or box-elder and from 
melons. 

More sugar is now derived from beets than from any other 
single source. 

The manufacture of cane sugar is an important industry 
of many countries and only the general principles involved 
in the operations can here be referred to. 

From the cane the juice is extracted by crushing between 
rollers. Lime is added to the juice to prevent the inversion 
of the sugar. It is also generally subjected to the action of 
sulphurous acid to prevent fermentation. The juice is then 
heated to coagulate albuminous matter, which rises to the 
surface as a scum. The liquid is then separated from the 
scum and sediment, and evaporated to the crystallizing 
point. It is then allowed to cool and crystallize and the 
molasses drained off. This product is the raw sugar and has 
to be still further treated to obtain refined sugar. The 
refining is accomplished by re-solution in hot water, filtra- 
tion, and decolorization by passage through animal charcoal 
and evaporation in vacuum pans. The steps in the prepara- 
tion of beet sugar are essentially the same as in cane sugar 
but the juice of the beet is generally extracted by the 
"diffusion" process and not by mascerating the beets and 
pressing the pulp. For diffusion the beets are cut into thin 
slices and subjected to the action of warm water by which 
the juice is effectually extracted. The diffusion process has 
also been applied to the cane. 

Nearly all the beet sugar is made in Continental Europe. 



301 

The cane sugar is derived from many localities, but mainly 
from Cuba, Java, Manila, Brazil, Mauritius, and Louisiana. 

Properties of Sugar. Many of the properties of sugar are 
too well known to mention. It melts at 160° C. and forms an 
amorphous mass upon cooling. If kept at that temperature 
for some time it is converted without loss of weight into 
dextrose and an uncrystallizable syrup, leevulosan (C 6 Hio0 5 ). 
At a higher temperature it loses water and becomes brown, 
yielding according to Bloxam, "caramelan" (Ci 2 Hi 8 0g). Cara- 
mel is composed of this body mixed with other substances 
and is the result of the action of heat upon sugar. Caramel 
is largely used to color alcoholic liquors. 

Maltose; C l . i W 22 O xt . This body results from the action of malt 
upon starch. The germinating grain (malt) contains a peculiar sub- 
stance "diastase" which causes the starch to undergo hydrolysis, 
forming maltose and dextrose. Crystallized out of alcoholic solution 
maltose has the same composition as cane sugar, but from aqueous 
solution its formula is C 12 H 2 . i 11 ,H 2 0. It becomes anhydrous at the 
boiling point of water. 

Amyloses, Starch and Cellulose (C 6 Hio0 5 )n. The best 
known and the most important members of the amylose 
group are starch and cellulose. 

Starch (C 6 Hi O 5 )n. This is one of the most widely diffused 
bodies of the organic kingdom. It occurs in all plants that 
have been examined except certain fungi and abundantly in 
the seeds of plants, especially of those cereals used for food. 
Rice, wheat, and Indian corn contain it in largest proportions. 

Fully two-thirds or more of the food of mankind is de- 
rived from the carbohydrate group and starch furnishes much 
the largest proportion. 

Starch is necessary to the growth of plants and its presence 
in the seeds affords nourishment to the young sprouts. 

Preparation of Starch. In the United States starch is 

generally prepared from maize (Indian corn); in England 
from rice and potatoes; on the continent of Europe from 



■- 

potatoes and wheat. The obje : in ea }h ease is of eours^ to 
se] . ate the starch from the other constituents. The outline 

of the method adopted in this country will give an ide 
the principles involved in all eases. 

The cleaned grain (maize) is steeped in water for about 
30 hours until soft enough to grind. It is then crushed by 
rollers or ground between mill-: nes and washed upon sieves. 
The pulpy mass left upon sieves may be reground and sub- 
jected to a second washing. The milky liquid carrying the 
starch flows int : inclined boxes known as starch- 

tables during which time the starch granules are dei - 
The liquid passing on from the starch-tables flows into tanks 
in which are leposited certain nitrogenous matter. This lat- 
ter is mixed with the husk- from the sieves and worked up 
for cow and pig-ieed. 

For further increasing the purity of the starch by the 
removal of the nitrogenous matter it is washed in a dilute 
solution of alkali (caustic soda) and again allowed to settle, 
the escaping liquid carrying off the nitrogenous matter, oils, 
etc. The starch is again thoroughly washed to remove 
alkali. The several subsequent operation are mechanical. 
The reports fi m -onie of the larg^- American factories show 
a yield of starch equal to one-half the weight of the maize 
employed. This indicates a heavy loss of the total starch 
contained. Single factories eonvert from five to twenty 
thousand bushels of eorn daily. 

The starch from the potato may be tained by seep- 
ing, crushing, and washing without the use of alkali. Rice 
contains the greatest percentage of starch but the use of 
alkali is necessary to separate it from the other constituents 
of the grain. In the manufacture of starch-sugar or dex- 
trc se already referred to. the first step in the prej aration of 
stai sh is that above describe .. 

The finest qualities of starch are use 1 for food, for mak- 
ing sugars and syrups, for sizing the finest papers, and for 



303 

laundrying. The other varieties are largely used in the in- 
dustrial arts, for weavers' dressing, for thickening mordants, 
etc. Besides the edible starches obtained from rice, pota- 
toes, maize, and wheat, there are several other forms. 

Arrow-root. The starch known under this name is ob- 
tained from the root of several kinds of plants widely dis- 
seminated in the tropics. The most important of these 
flourish in tropical America from Mexico to Brazil and in 
the West Indies. They belong to the genus Maranta. The 
Brazilian arrow-root is frequently called cassava-starch. 

Tapioca. This is a specially prepared form of the Cassava 
starch, other starches are obtained from the roots of various 
plants in widely separated places, Africa, Australia, East 
Indies, and China. 

Sago. This is starch obtained from the pith of certain 
varieties of the palm, indigenous to the East Indian archi- 
pelago and the adjacent regions. These last named starches 
differ materially from the grain starches in that they are 
more nearly pure starch, more readily gelatinize, and are 
thought to be more easily assimilated by the human system. 

Characteristics of Starch. To the naked eye starch 
appears as a white glistening powder but under the micro- 
scope it is seen to have an organized structure, to consist of 
granules generally ovoid, which are composed of concentric 
layers. The starch granules from different sources differ in 
appearance. The granules vary very much in size, those 
from the potato being 1-300 of an inch in the longest diameter 
while those from certain plants, as cactus, are not over 1-10000 
of an inch. Starch is without odor, is insoluble in cold water 
and consequently without taste. The granules consist of 
starch-cellulose or farinose in the outer layers, the exterior 
layer being probably wholly composed of it. This cellulose 
is insoluble in cold water. The interior of the granules is 
partially soluble in cold water and is called granulose. The 



304 

insolubility of the outer layer prevents the action of cold 
water upon starch. When a mixture of starch and water is 
heated to about 70° C. the granules burst, the -granulose is 
dissolved to a viscous liquid slightly opalescent, due to the 
undissolved cellulose. The solution becomes gelatinous on 
cooling and gum like when dried. Iodine colors starch 
intensely blue and the action takes place upon the granules 
intact as well as upon the paste. Starch heated for some 
time up to about 200° C. is partially converted into dextrin. 
The conversion into the soluble form is important in the 
preparation of foods. 

Dextrin; (C 6 H 10 O 5 j n . This body has the same formula as starch.. 
It may be prepared by heating starch with dilute acids or by heating- 
dried starch to a high temperature. Dextrin is soluble in water. 
There are several modifications of dextrin which are used as substi- 
tutes for gum . 

Gums. These are amorphous bodies occurring in many plants. 
They are insoluble in alcohol but are soluble in water and form a vis- 
cous mass with it. Those which form a clear solution with water are 
real gums; the others vegetable mucilages. 

Cellulose (C 6 Hio0 5 )n. This substance is the principal 
ingredient in the framework of plants. It constitutes the 
walls of plant-cells and forms a large proportion of the 
solid parts of all vegetables. Woody- tissue consists of the 
membranous cells together with encrusting material. When 
all encrusting material has been removed by solvents the 
cellulose is left. 

Fine linen and cotton are composed of nearly pure cellu- 
lose, the treatment to which the fibre is subjected having 
removed nearly all the other material. 

Pure cellulose is insoluble in nearly all ordinary solvents, 
is tasteless, and for a long time was thought to be absolutely 
innutritious, but this point is now thought to be doubtful. It 
is known to constitute a large part of the food of beavers. 
Cellulose is soluble in an ammoniacal solution of cupric 



305 

hydroxide (Schweitzer's reagent.) Cellulose is not colored 
by iodine. 

If unsized paper be steeped for a few seconds in a mixture 
of strong sulphuric acid and half its volume of water, and 
then washed with water and dilute ammonia it is converted 
into a sort of parchment. It has the same composition as 
cellulose and is called vegetable parchment. It is trans- 
lucent, much stronger than paper, is very useful in diffusion, 
and is largely used for baggage labels. It is not easily torn 
and withstands rain. 

Strong sulphuric acid converts dry cellulose into a gummy 
mass, which by the proper manipulation may be converted 
into dextrose and then into alcohol ; linen rags may thus be 
converted into alcohol. 

VEGETABLE COLORS. 

The vegetable kingdom exhibits great beauty and variety of color 
but the compositions of the coloring principles have been determined in 
only a few cases and only a few of the colors obtained directly from 
plants find application in the arts. 

The most universally distributed color in nature is that of green 
and is due to the presence of chlorophyl which occurs in all the green 
parts of plants. Its composition is not known though iron is supposed 
to be a constituent of it. Wax and other substances are associated 
with it forming chlorophyl grannies. 

The blue coloring matter present in certain flowers has been called 
cyanin. It is made red by acids, consequently blue flowers can not 
contain acid juices, while red flowers do. Bloxam attributes the color 
of certain grapes and red wine to cyanin. 

Saffron, Turmeric, Madder, and Litmus are all vegetable colors. 
The litmus is obtained from certain varieties of lichens. It is made blue 
by alkalies and red by acids the original color being a purplish rod. 

Lac .is a red coloring matter extracted from a resin of the same name 
obtained from a tropical plant. 

Carmine is a red dye obtained from the cochineal, the dried body of 
a species of insect which feeds upon a certain variety of cactus. 

Indigo. This is obtained from the indigo plant growing chiefly in 
India, but also in China. Egypt, and South America. It has been known 
as -,\ dye for many hundreds of years. It does Dot exist ready formed 

in the plant but is the product of the alteration of the substance 
20 



306 

known as indican which is nearly colorless. The indigo is obtained by 
ma§cerating the plants in water and allowing them to ferment. The 
indican is converted first into white indigo and then by oxidation into 
the common or blue indigo. 

The above named dyes are all composed of carbon, hydrogen, and 
oxygen except indigo which in addition contains nitrogen. Indigo is 
extensively employed for dyeing woolen fabrics. 

ALBUMINOUS SUBSTANCES. 

This term includes a number of complex bodies found in vegetable 
and animal organisms all of which in addition to carbon, hydrogen, 
and oxygen contain nitrogen and most of them sulphur. Not much is 
known in regard to the constitution of these bodies, their molecular 
formula? not having been determined. The percentage numbers indi- 
cate great conformity in chemical composition and the same conform- 
ity is shown in their general properties. The proportion of the nitro- 
gen to the carbon, hydrogen, and oxygen is much higher than is usual 
in organic bodies. 

The albuminous substances are sometimes divided into two classes 
— albuminoids and proteids. The second more closely resemble com- 
mon egg-albumin and are generally coagulated by heat, the first like 
bone-cartilage, yield gelatine with boiling water and are sometimes 
termed simply gelatinous bodies. Again both classes are sometimes 
included under the term proteids. 

Only a few of the most typical and common of the albuminous sub- 
stances will be mentioned here. 

Gelatine, Glutin. When the skin, tendons, and organic matter of 
the bones of the animal body are subjected to the long continued action 
of boiling water a solution is obtained which on cooling solidifies to a 
tremulous transparent mass which becomes hard and brittle on drying. 

Cold water softens but does not dissolve gelatine. It is dissolved 
in hot water and the solution gelatinizes on cooling. 

Tannin precipitates gelatine from its solution. The tissues which 
yield gelatine unite with tannic acid forming an insoluble non-putresci- 
ble compound, or leather. 

Isinglass is a pure form of gelatine obtained from the bladder of 
the sturgeon and other fish. 

Glue and size are impure gelatines made usually from th#parings 
of hides. 

Gelatine is largely used in food preparations, for clarifying wines, 
and in photography. Gelatine is sometimes called glutin. 

A gelatinous body closely resembling the animal gelatine is also 
obtained from silk. 

Albumins. There are several varieties of albumin differing but 
slightly from each other. These bodies are found in the blood, muscles, 



307 

nerves, and other organs of animals and also in nearly all parts of 
plants, especially the seed. It is thought that probably these bodies 
are synthesized by the plant and that they are taken up and appro- 
priated by the animal with but slight change. 

Egg-albumin. This exists in aqueous solution in the egg and is 
one of the most common varieties of albumin. It is coagulated and 
rendered insoluble in water by heat. Alcohol and ether also precipi- 
tate it from solution. The raw albumin of the egg does not affect 
silver but this metal is tarnished by cooked eggs, which also give a 
faint odor of sulphuretted hydrogen, indicating some decomposition in 
the cooking by which H 2 S is liberated. 

Serum T albumin. This is abundantly present in the blood and other 
animal secretions. It closely resembles egg-albumin but is not precipi- 
tated by ether. 

Plant-albumin. This occurs in nearly all vegetable juices, it is 
coagulated by heat and closely resembles the egg and serum albumins. 

Myosin. This is the albuminous substance present in solution in 
the sheaths of muscular fibres. Its spontaneous separation from the 
plasma after death produces the rigor mortis. 

Fibrin. Blood fibrin is the albuminous substance which separates 
from the blood during coagulation or clotting. It appears to be formed 
from soluble albumin in the blood, by a change which is set up when 
the blood is removed from the vital influences. The clot is red, due to 
the entanglement of the red corpuscles in the fibrin. By washing, the 
fibrin may be separated into elastic filaments which become hard and 
brittle upon drying. 

Vegetable Fibrin. This occurs in the undissolved state in plants 
and especially in the cereal grains. When wheaten flour is kneaded 
upon a cloth with water the soluble albumin and starch are separated 
and a tenaceous mass remains which is called gluten. When this 
gluten is boiled with dilute alcohol a portion is left undissolved and is 
called vegetable or plant fibrin. 

Milk Casein. Casein occurs in the milk of all mammalia, most 
plentifully in that of the caraivora. It is the chief constituent of the 
curd of milk. It exists in solution in the milk due to the presence of a 
little alkali. If the alkali be neutralized by the souring of the milk or 
the addition of a little acid the casein is separated. The most striking 
property of the casein is its coagulability by rennet, the mucous mem- 
brane of the calf's stomach. Casein does not coagulate spontaneously 
by heat. 

Vegetable Casein; Legumin. This substance is found most abund- 
antly in 1 he seeds of leguminous plants as beans and peas. It closely 
resembles animal casein and its solution is coagulated by rennet. 



308 

Gluten. It is stated above that gluten is the name given to the 
tenacious mass left when wheaten flour is kneaded upon a cloth with 
water. When treated with boiling dilute alcohol a portion of the 
gluten is left undissolved and is called vegetable fibrin. As the alco- 
holic solution cools, a white flocculent precipitate is deposited which 
closely resembles the casein of milk, it is called mucedin. On adding 
water to the cooled solution a third substance is precipitated, which 
closely resembles serum albumin and is called glutin or gliadin. 

It is pertinent to recall here the fact that the albuminous sub- 
stances of the animal organisms have their counterparts in the 
vegetable kingdom. 

ALKALOIDS. 

This name is given to a large class of nitrogenous vegetable com- 
pounds of a basic character. Many of them are of great medicinal 
importance because of the powerful action they exert on the animal 
system. They all contain carbon, hydrogen, and nitrogen, and nearly 
all contain oxygen in addition. They are soluble in alcohol and gener- 
ally have a bitter taste. 

Caffeine ; Theine. This is the principal alkaloid of tea and coffee in 
which it is thought to be present as a salt of some variety of tannic 
acid. Tea also contains a small quantity of some other alkaloids. 
Caffeine is composed of carbon, hydrogen, oxygen, and nitrogen. 

The fragrance which distinguishes prepared coffee does not belong 
to the raw berry but is developed by the roasting. In the same way 
the aroma of the tea is developed by heat during the drying of the 
leaves. Each is due to a volatile aromatic oil produced by the heat. 

Nicotine. This is one of the alkaloids that does not contain 
oxygen. It exists as a salt of malic acid in the leaves and seed of 
tobacco. It is a volatile oily liquid. Nicotine and its salts are power- 
ful poisons. Tobacco may contain from one to eight per cent of 
nicotine but seldom over four. Tobacco contains an unusual percent- 
age of mineral salts. This explains the large amount of ash it leaves 
upon burning. This ash may amount to one-fifth the weight of the 
dried leaf. The salts are mainly the malate, citrate, and nitrate of 
potassium. The presence of these salts, especially the last, explains the 
smouldering combustion which these leaves undergo. 

Opium. This is the thick juice which is obtained from the capsules 
of the opium-poppy (popaver somniferum). It is a complex substance 
containing a large number of bases, one of the most abundant and 
best known of these is morphine. 

Morphine. This is obtained from opium in which it is present often 
to the extent of ten per cent. It is a white powder, soluble in 500 parts 
of water and has a bitter taste. Its formula (C 17 H 19 N0 3 ) shows it to 



309 

contain carbon, hydrogen, oxygen, and nitrogen and representing it by 
"M," the common medicinal form of morphine is MHO, the hydrochlo- 
ride of morphine or the muriate of morphia. 

The alkaloid present in opium in most abundance next to morphine 
is narcotine. 

Quinine. The bark of several species of the cinchona order contain 
a number of alkaloids usually associated with some vegetable acids. 
The best known of these is quinine and this is the most important of 
the alkaloids. It is immensely used as a febrifuge. It is found most 
abundantly in the yellow cinchona or Peruvian bark. 

Quinine crystallizes in small crystals and to the naked eye appears 
as a white powder. It requires about 2000 parts of water to dissolve 
it and its solution is alkaline and bitter. Its composition is indicated 
by the formula C 20 H 24 N 2 2 . The form of quinine generally used in 
medicine is the basic sulphate, which may be represented by Q 2 H 2 S0 4 , 
Aq. in which Q stands for the formula above given. 

The cinchona barks were introducd into Europe from Peru in the 
first half of the seventeenth century by the wife of the viceroy of Peru, 
the countess of Chincon from whom they received their name. The cin- 
chonas are indigenous to the slopes of the Andes between 7° N. and 20° 
S. The barks richest in alkaloids grow at an altitude between 6000 and 
12000 feet above the sea. The most highly prized cinchonas have been 
successfully cultivated in Java for nearly fifty years. 

Strychnine. This is obtained from the seeds and bark of the mix 
vomica, from St. Ignatius' bean, and from other tropical plants. It is 
slightly soluble in water, is bitter, and fearfully poisonous. It is said 
that it can be detected by its taste when it is dissolved in a million 
parts of water. 

Cocaine. This is obtained from the leaves of certain varieties of 
coca. Cocaine, in aqueous solution, is employed as a local anaesthetic 
and finds extended use in minor surgical applications. In small doses 
it acts as a stimulant and is one of the most insinuating of the poison- 
ous drugs. The medicinal form most generally employed is the hydro- 
chloride, BHC1. 



IMPORTANT INDUSTRIAL APPLICATIONS 
OF CHEMISTRY. 



CALORIFIC VALUE OR POWER. 

The calorific power of a substance is the amount of heat 
evolved due to its combustion. The calorific value of the 
ordinary hydrocarbon fuels may be approximately calculated 
from their compositions. Many of these fuels contain oxy- 
gen and it is assumed that the heat developed by the perfect 
combustion of the fuel is equal to that due to the perfect 
combustion of the carbon and so much of the hydrogen as is 
in excess of that necessary to form water with the oxygen 
present. In other words it is assumed that the oxygen pres- 
ent is combined with hydrogen in the form of water and that 
the oxidized hydrogen adds nothing to the heating power. 
This form of computation is illustrated below. 

Example. — Required the calorific value of 75 pounds of wood. 
Molecular formula of wood is taken as C 6 H 9 4 =C 6 H(H 2 0) 4 , molecular 
weigh t=145. 

{72 pounds of C ; 1 pound of C produces 
8080 units of heat. 
1 pound of H ; 1 pound of H produces 
34462 units of heat. 
72 pounds of H,0. 

Units of heat produced by the carbon in burning=72X8080=581760. 

Units of heat produced by the hydrogen in burning= 1X34462=34462. 

Total heat produced by the 145 pounds of wood=616222. 

616222 

Hence the calorific value of 75 pounds of \vood= " X75— 318735, 

1 ■+•> 



312 

CALORIFIC INTENSITY. 

Calorific intensity may be defined as the temperature to 

which the heat generated by the burning fuel could raise the 

products of its own combustion. In the case of pure carbon, 

burning to carbon dioxide, the calorific intensity may be ob- 

C 
tained from the following formula: T=^q, in which T is 

the calorific intensity, C the calorific value, W the weight of 
the carbon dioxide produced, and S the specific heat of the 
carbon dioxide. In the above formula it is assumed that 
the specific heat of carbon dioxide is constant at all tempera- 
tures. In such computations it should be remembered that 
the specific heat of gases is less at constant volume than at 
constant pressure so that calorific intensities would be greater 
at constant volume. 

In the case of fuels containing hydrogen or hydrogen and 
oxygen in addition to carbon, there are certain considerations 
that do not enter the problem just given. In determining 
the calorific power of hydrogen the vapor of water resulting 
from its combustion was condensed in the calorimeter and the 
heat which was latent in the vapor became sensible and was 
properly included in the calorific value, but when the vapor is 
no longer condensed this heat can not be considered 
in the production of temperature and must be deducted from 
the calorific value in the formula for calorific intensity. 

In fuels containing oxygen the oxidized hydrogen exist- 
ing or supposed to exist as water is vaporized by part of the 
heat of combustion. This number of heat units must also 
be deducted from the calorific value of the fuel in the formula 
for intensity. 

Note. In addition to these deductions there is another slight deduc- 
tion which should be made from the calorific value. In the computation 
of the temperature produced, the initial temperature is 0°C. ; between this 
point and the boiling point the specific heat of water is greater than 
that of steam in the proportion (approximately) of one to five-tenths, 
so that for each pound of steam produced there should be further 
deducted 100X.5=50 units of heat. 



313 

The formula for the calorific intensity of fuel, like wood, 
containing hydrogen, carbon, and oxygen, is 

T _ C-(B) 

1 ~ WS+W,S,+etc. 
in which T is the calorific intensity, C the calorific value, B 
the latent heat of steam produced, which comes partly from 
the combustion of the free hydrogen in the fuel, partly from 
the combined oxygen present as water and in part composing 
the fuel; W and W,, are the weights respectively of the car- 
bon dioxide and the water vapor produced; S and S,, are the 
specific heats respectively of the carbon dioxide and the 
water vapor. 

Example. — Required the calorific intensity of wood burned in a full 
supply of oxygen. When burning in full supply of oxygen, C+0 2 = 
C0 2 and H 2 -fO=H 2 0; atomic weights of carbon, hydrogen, and oxy- 
gen are 12, 1, and 16, hence 12 parts by weight of carbon require 32 
parts by weight of oxygen and produce 44 parts by weight of carbon 
dioxide; 2 parts of hydrogen require 16 parts by weight of oxygen and 
produce 18 parts by weight of water, hence 1 part of carbon produces 
3% parts of carbon dioxide and one part of hydrogen produces 9 parts 
of water. It has been seen by the formula, that in 145 parts of wood, by 
weight there are 72 parts of carbon, 1 part of hydrogen, and 72 parts 
of water. 

By combustion the one part of hydrogen produces nine parts 
of water, this with the seventy -two parts of water in the wood gives 
eighty-one parts of water to be evaporated, the latent heat of which 
is 81X537=43497. 

The 72 parts of C in the wood produce 264 parts of carbon dioxide. 

( C0 2 r=.22 
The specific heats are approximately \ 

{ H.,0 (vapor) =.5. 

The calorific value of 145 pounds of wood as determined above is 
616222. 

The heat rendered latent by the evaporation of 81 parts of 

water = 43497 

Heat units availablefor heating products of combustion... = 572725 

Number of heat units to raise the products of combustion from 145 
pounds of wood 1° C.-=264X.22+81X.5, hence the calorific intensity of 

572725 
W00<3 iS 2«rX^2+SlXT5«) = 5S0!,O+ - 

The calorific intensity is independent of the weight of the body 
burned but is dependent upon the time and the atmosphere in which 



314 

the combustion takes place, being greatest in oxygen. If the combus- 
tion takes place in the air which is usually the case, the calorific 
intensity is lowered because of the large amount of nitrogen which has 
to be heated. The complete combustion of carbon requires 2% times 
its weight of oxygen and hydrogen requires 8 times its weight of 
oxygen. In the above example of wood the 72 parts of carbon will 
require 192 parts of oxygen and the 1 part of hydrogen would require 8 
parts of oxygen, making necessary 200 parts of oxygen. Taking the 
formula of the atmosphere as 4N+0, we see that for 10 parts by weight 
of oxygen there are present 50 parts of nitrogen or 3% parts of nitrogen 
for one of oxygen. We have seen that 145 parts of wood would require 
200 parts of oxygen for combustion; in supplying this oxygen by 
means of the atmosphere there would be introduced 3% times as much 
nitrogen or TOO parts of nitrogen. The specific heat of nitrogen is 
about .25. The formula for the calorific intensity in the air would be 

T— 572725 — 2oqq° C 

204X. 22+81 X. 5+700 X. 25 

In all ordinary furnaces in order to maintain the draught, much 
more air has to be introduced than would be required to supply the 
necessary oxygen. This extra amount of air still further reduces the 
intensity. In addition to this extra amount of air, all the heat can not 
be applied to heating the products of combustion as assumed in the 
discussion. Part of the heat is lost by radiation and some is lost in 
heating the grate and other parts of the furnace and in heating the 
unburned fuel. Again complete combustion does not always take 
place. From these considerations it is evident that the computed 
calorific intensity is only approximate. 

GLASS MAKING. 

The manufacture of glass is a very ancient industry, the 
earliest examples being 1 of Egyptian origin. A lion's head of 
glass found at Thebes and now in the British Museum bears 
an inscription which places its date at 2400 B.C. In the 
tombs of Beni Hassan dating at least 2000 B.C. the process of 
glass blowing is represented. These two facts prove that 
glass was made more than four thousand years ago. 

Glass is a mixture of several insoluble silicates and is des- 
titute of crystalline structure when not too slowly cooled. 
One of the silicates present is always that of an alkali metal, 
potassium or sodium, and with these are associated one or 
more of the silicates of calcium, barium, lead, iron or zinc. 



315 

The mixtures of these silicates display properties that are 
not possessed by the single silicates. The presence of alka- 
line silicates is necessary in the glass, for these silicates when 
fused dissolve silica readily, fuse more easily than any other 
class, and exhibit less tendency to crystallize on cooling. 
The silicates of the other metals named are more infusible 
and less readily acted upon. By mixing the silicates in the 
proper proportions the requisite properties are obtained in 
the glass. 

The most valuable and important properties of glass are 
its transparency, its plasticity before complete fusion, and 
its permanency. There are a great many kinds of glass dif- 
fering more or less distinctly from each other depending 
upon the proportions of the constituents. The two most im- 
portant divisions may be based upon the silicates present. 

First, The glass which contains alkaline and calcium 
silicates, and second, that which contains alkaline and lead 
silicates. To the first class belong the common window 
glass, plate glass, and crown glass; to the second belong the 
flint or crystal glass and the material of artificial gems. 

Common window glass is composed essentially of sodium 
and calcium silicates and is made by fusing together the 
proper proportions of sand, calcium carbonate, and sodium 
carbonate. It usually contains a little aluminum silicate 
owing to lack of purity in the materials employed. 

Plate glass has essentially the same composition as win- 
dow glass but is made from purer materials. Usually some 
potassium carbonate replaces some of the sodium as an 
ingredient. 

Croivn glass is composed of the silicates of potassium and 
calcium and is made by fusing together the proper propor- 
tions of sand, potassium carbonate, and calcium carbonate. 
Potassium is less likely to impart color to the glass than 
sodium. This glass is generally employed for optical pur- 
poses. 



316 

Bohemian glass contains the same constituents as crown 
glass but has a larger proportion of silica to which is due its 
greater permanency and infusibility. 

Lead or Flint Glass. This glass is made by fusing to- 
gether in proper proportions silica, lead oxide, and potas- 
sium carbonate. The oxide of lead generally used is the 
Pb 3 4 . The higher oxide is preferred because the excess of 
oxygen serves to oxidize any organic impurities that might 
accidentally be present. 

Colored glass is made by fusing certain metallic oxides 
with the ingredients of any of the above-named glasses. 

The glass from which bottles are generally made has 
essentially the same composition as common window glass 
though containing less sodium and in addition some iron 
silicate to which its color is due. 

The red oxide of copper gives a red color to glass ; cobalt 
oxide a blue color; oxide of manganese an amethyst color. 

Production of Glass. The principle of glass manufacture 
is simple. The materials of the glass are fused together and 
the silica combines with the metallic oxides forming silicates. 

The fusing was formerly accomplished in large pots or 
crucibles of refractory fire-clay. The pots varied in size from 
three to five feet high and two to four feet in diameter. A 
number of these pots were accommodated in a single furnace 
and heated by gaseous fuel which played around the pots. 
With lead-glass covered pots were required to prevent the 
reduction of the lead to the metallic state by the gases of the 
fuel, in other cases the pots were open. 

In the past dozen years the pot furnaces have been 
largely replaced by the open-hearth or tank furnaces, this is 
especially so in the manufacture of bottles and of window 
glass. Some of these modern furnace's are of astounding 
dimensions being from sixty to seventy-five feet long, from 
four to six feet deep and from ten to twelve feet wide, and 



317 

capable of containing over four hundred tons of melted 
glass. 

The fused constituents of the glass are converted into a 
great variety of finished products by processes which differ 
depending upon the kinds of products desired. In general 
after the constituents are fused together the manufacturing 
operations may be grouped into four. 

1st, Croivn and Sheet Glass. A hollow glass sphere is 
obtained by blowing and this for crown glass is converted 
into a flat disc by rapid rotation. For sheet glass the globe 
is opened and extended into a cylinder, then split longitudi- 
nally, spread into a sheet, and flattened by suitable tools. 
Window glass is generally made in this way. 

2nd. Plate glass by pouring the fused glass upon a flat 
table and subsequently grinding and polishing it. 

3rd. Hollow Ware. Under this are classed all kinds of 
bottles as well as the more delicate glasses, vases, etc. Bot- 
tles are always made by blowing the glass into moulds, both 
the external and internal portions of the bottle assuming the 
shape of the mould. The process is a very rapid one; a 
" set " of five men generally work together in moulding bot- 
tles and they usually average two or three finished bottles 
per minute. 

Wine-glasses, vases, pitchers, etc., are made by blowing 
and hand manipulation but little use being made of patterns 
or moulds. Such ware requires the greatest manual skill 
and can only be fashioned by the most expert workmen. 

4th. Pressed Glass. Many kinds of glass-ware for domes- 
tic purposes are now made by moulding into shape by press- 
ure. The external form is given by the mould and the 
internal by the shape of the plunger. This process has 
brought into use a very cheap ware suitable for nearly all 
domestic purposes. The lead glass was found most suitable 
for pressed ware but to diminish cost the lead oxide has been 



318 

replaced by barium carbonate which gives a clear glass suit- 
able for this manufacture. 

All finished glass products require to be annealed to avoid 
spontaneous fracture. 

By using a certain kind of glass called strass as a base all 
the precious stones can be imitated except opal. The pro- 
duction of artificial gems is an important feature of glass 
manufacture. 

De vitrified Glass. Certain kinds of glass containing but little alka- 
line silicate may be made to partially crystallize by heating nearly to 
the fusing point and then cooling slowly. It thus becomes opaque and 
is sometimes called Reamur's porcelain. It may be made transparent 
by refusion. 

Soluble Glass. If silica be fused with an excess of sodium or potas- 
sium carbonate it forms a glass which is soluble in water — a solution 
of which is sometimes used in making artificial stone. If sand be 
moistened with it and pressed into shape and heated highly, the glass 
fuses and binds the whole together. It is also used to preserve nat- 
ural stone from decaj^, in mural painting, and in rendering wood non- 
inflammable. 

The glass industries of the United States are mainly cen- 
tered in New York, New Jersey, and Pennsylvania. The 
abundance of suitable sand in this country affords marked 
advantages for this industry. Nearly all the sand employed 
in glass making is mined as sand-stone and this is crushed 
preparatory to use. The sands of the United States suit- 
able for making the finest grades of glass are abundant and 
found in many of the states. Among the beds most exten- 
sively worked are those of Berkshire County, Mass., Juniata 
County, Penn., Morgan County, W. Va., and some in Illi- 
nois and Missouri. 

MANUFACTURE OF POTTERY. 

Pottery in its widest sense includes all articles in which 
clay is the main ingredient and which have been hardened 
by the application of heat, natural or artificial. The chemi- 
cal principles involved in the manufacture of a few import- 
ant kinds will be given. 



319 

The properties of clay which make it the basis of all 
forms of pottery are its plasticity when moist which enables 
it to be kneaded, and its subsequent hardness when heated. 

The two most general divisions of pottery are the glazed 
and the unglazed forms, of the first, porcelain may be taken 
as the most characteristic variety and highest type. Porce- 
lain is made from the purest clay or kaolin, but a vessel made 
from clay alone would shrink and lose its shape in drying 
and be liable to crack in the kiln. To prevent this, other sub- 
stances are mixed with the clay of the ware which cause it to 
retain its form and which fuse at the temperature of the 
furnace and bind the whole into a homogeneous compact 
mass. These fluxing ingredients differ at different manu- 
factories and to these differences are due the various kinds 
of porcelain. 

In the celebrated Sevres porcelain there is added to the 
kaolin, feldspar and a little chalk. In the Meissen porcelain 
there is added feldspar and ground waste, porcelain. The 
other fluxes most commonly used in porcelain are sand, bone- 
ash, and gypsum. In each case the clay and other materials 
are brought to the finest state of subdivision and usually held 
suspended in water. The creamy liquids are then mixed in 
the proper proportions, allowed to settle, separated from the 
water, and the paste thoroughly kneaded. The proper pro- 
portions of the ingredients may be brought together in the 
dry state and the whole agitated together in water. In any 
case after the mixed ingredients are separated from the water 
the mass is usually left to stand for considerable time which 
improves the quality of the clay. This result is believed to 
be brought about by the oxidation of any organic matter 
present and to physical change brought about by drying and 
shrinkage which affect the plasticity of the clay. When 
ready for the workman the clay is moulded into the required 
shape by various forms of potters' wheels, jiggers and lathes, 
but principally by moulds. The most perfect specimens are 
always finished by hand. 



320 

The moulded articles are dried by exposure to the air, then 
packed in cases or saggers and subjected to a comparatively 
low heat of the kiln. The articles are thus sufficiently heated, 
dried, and hardened to receive the glaze without danger of 
breaking. The glaze for the porcelain must be similar to the 
material added for fluxing the clay. The glaze for the Sevres 
porcelain is ground feldspar and quartz, for the Meissen 
ware it is clay, silica, and ground ware. The glaze material 
is very finely ground and evenly applied to the surface of the 
ware by dusting, fe«t more generally the glaze is suspended 
in water and the article is deftly dipped in the water and 
removed. Enough of the material of the glaze adheres to 
the surface of the ware. The ware is now completely 
hardened and the glaze fixed by exposure for many hours to 
a high temperature ; the ware for this purpose is packed in 
saggers as during the preliminary heating. 

The Sevres and Meissen ware come under the head of 
hard porcelain. Hard porcelain has several characteristics 
which distinguish it from other forms of glazed ware. The 
glaze is thin and graduates imperceptibly into the body of the 
ware ; the ware is translucent and breaks with a chonchoidal 
fracture. Hard porcelain is unique in that the ware is sub- 
jected to but one burning, the ware being hardened and the 
glaze fixed at the same time. 

With all other forms of glazed ware there are two "firings," 
one known as the biscuit firing which hardens the ware and 
the other fixes the glaze upon it. Statue porcelain is a true 
hard porcelain but is not glazed. 

English soft porcelain is more fusible than the hard porce- 
lain and the glazing requires a separate "firing." 

STONEWAEE. 

This is a coarse kind of porcelain made from impure 
material. For glazing, the ware is coated with fine sand by 
dipping it in water holding the impalpable sand in suspen- 
sion. During the firing of the ware damp salt is thrown 



321 

into the kiln. Decomposition ensues by which hydrochloric 
acid and sodium oxide are formed, the latter combines with 
the silica and forms sodium silicate which fuses and consti- 
tutes the glaze. 

Decorating Porcelain. A uniform color can be given to 
the ware by mixing the proper mineral pigment with the 
glaze. Colors in pattern and design are put upon the ware 
after glazing and fixed by another firing by which the pig- 
ment is fused and firmly fixed upon the ware. 

The most expensive and finest decorating is done by hand, 
but the design is usually engraved on a copper plate and a 
print taken from it in mineral colors on a sheet of tissue 
paper. By gentle pressure the print adheres to the ware 
and after a short time the paper can be removed, the firing 
then fixes the design. 

The above general description of glazed ware applies usu- 
ally to that of all countries, but only on the continent of 
Europe is made the hard porcelain by a single firing. In 
this country the white wares suitable for household purposes 
may be fitly placed in four grades. The finest is a true por- 
celain having a vitreous translucent body and a perfect ac- 
cordance between glaze and ware. 

Pottery kilns are solidly built circular structures of ma- 
sonry rising to a crown inside and surmounted by a shaft or 
dome to secure draught. Around the base are the fire-places 
which open into the kiln. Except for hard porcelain the 
ware is fired twice, the first is called biscuit firing and re- 
quires the highest temperature and longest time. During 
this the body of the ware is solidified into a homogeneous 
mass and when withdrawn from the kiln it rings when struck 
almost like metal. The object of the second firing is to 
fuse and fix the glaze and is known as the "glost " tiring. 
This requires less time and the temperature is not so high as 
in the first firing. 

21 



322 

The decorations in design are fixed by a third firing' which 
requires less time than either of the other two. 

The porcelain industries in this country are centered at 
East Liverpool, Ohio, and at Trenton, New Jersey. The 
Rockwood potteries at Cincinnati are celebrated for their 
special ware, but it is a Fayence or porous ware. The Balti- 
more potteries also produce a porous ware, parian and ma- 
jolica, the latter being quite celebrated. The common forms 
of pottery are produced at many other places in the United 
States. 

Fire-ware. For the manufacture of fire-bricks and such 
articles of pottery as have to withstand a very high tempera- 
ture it is of course necessary to employ infusible material. 
Nearly pure clay is used for these purposes to which is 
added a little sand or ground ware of the same description to" 
prevent shrinkage. Crucibles are also made from clay 
mixed with an equal weight of graphite, such crucibles will 
withstand rapid changes of temperature with impunity. 

Common bricks are made from less pure varieties of clay 
which contain sufficient fusible material to "clinker" the 
bricks during the burning. 

EXPLOSIVES. 

An explosion may in the most general sense be defined as a sudden 
and violent increase in the volume of a substance. In this general 
sense the increase may or may not be due to chemical transformations. 
This definition includes all action by which there may be violent 
increase of volume ; thus a compressed gas or vapor is said to explode 
the action being mechanical and the result of the energy originally 
expended in bringing the gas to the compressed condition. In a more 
purely chemical sense an explosion may be defined as violent increase 
in the volume of a substance brought about by chemical transforma- 
tion set up in it, resulting in large volumes of heated gases. A body 
capable of undergoing this sudden change by chemical transformation 
upon the application of the proper disturbing cause is an explosive. 

For our purposes it will only be necessary to describe a few of the 
more important solid and liquid explosives. 

In these explosives the energetic action is due to the rapid conver- 
sion of a solid or liquid into gases occupying many times the volume 



323 

of the original substance, the increased volume being due to the change 
of state and the expansion by heat, resulting from the chemical trans- 
formation of the explosive. It is evident therefore that the energy of 
the action of an explosive will depend largely upon the rapidity of the 
chemical transformation by which it is converted into gas and vapor. 
The heat of the transformation when the products are the same is 
independent of the time but the temperature is greater the shorter the 
time. In the useful explosives the heat liberated and the gases pro- 
duced in the chemical transformation are mainly the result of oxida- 
tion processes, the bodies oxidized and the oxygen for the purpose all 
being present in the explosives themselves and the oxidation is inde- 
pendent of the oxygen of the air. The more important explosives all con- 
tain carbon as an essential element to be oxidized, other elements are 
also generally present. We may thus conceive explosions to be cases 
of a special kind of combustion. From a purely chemical view explo- 
sives can not be classified in a definite manner, but they may with some 
convenience and often are grouped into explosive mixtures and explo- 
sive compounds ; these divisions are not entirely distinct nor accurate. 

PREPARATION OF EXPLOSIVES. 

EXPLOSIVE MIXTUKES. 

These consist of a mechanical mixture of two or more 
ingredients which upon the application of the proper dis- 
turbing" cause undergo the transformation defined as an 
explosion. 

Simple Explosive Compounds. These are definite chem- 
ical compounds which from the proper disturbing cause 
undergo explosion. 

In such a compound the elements which enter the trans- 
formed products are all constituents of the single original 
body. In mixtures the elements so entering are con- 
stituents of the different composing ingredients. 

These simple explosive compounds may be associated 
with other bodies simple or compound in such manner as to 
produce modified results in the explosion. The substances 
resulting from such association supply instances of ex- 
plosives which might with equal propriety be put in either of 
the above classes. The great majority of the explosives 
however can be placed in one or the other group bearing in 



324 

mind the distinction that in explosive mixtures the in- 
gredients are capable of mechanical separation and in snch 
explosive compounds as contain more than one substance, 
they are not capable of separation by mechanical means. 

Explosives are also sometimes classed as high and low 
explosives. The former term being* applied to those ex- 
plosives in which the transformation is so rapid as to pro- 
duce a rupturing effect, the latter to those in which the 
transformation is less rapid and the effect, in general, one 
of propulsion. 

Explosives are again sometimes classed as explosives of 
the first and second order depending upon the time involved 
in the transformation. In explosions of the first order the 
time is very short the action being practically instantaneous ; 
in the second order the action is much slower the time being 
appreciable. Explosions of the first order are also termed 
detonations. Every explosive may be detonated and the 
order of the explosions graduate into each other. It is there- 
fore evident that the classification just given (into high and 
low explosives and explosions of the first and second order) 
are without scientific basis and are not more distinctive than 
the divisions into explosive mixtures and explosive com- 
pounds. The terms, however, have a general significance 
and are convenient. 

Explosive Mixtures. We have stated that an explosion 
may be considered as a combustion which is accomplished 
independently of the air and by the oxygen present in the 
explosive. In explosive mixtures one of the ingredients sup- 
plies the oxygen and the others the combustibles for oxida- 
tion. The most common oxidizing agents in explosive 
mixtures are the nitrates and chlorates. These salts form 
the basis for dividing the mixtures into the nitrate and 
chlorate mixtures. The former are the more important, the 
latter are however employed to a considerable extent in 
pyrotechny and in igniting other explosives. 



325 

Gunpowder. This substance is an intimate mixture of 
charcoal, sulphur, and nitre. For a satisfactory powder 
great attention must be paid to the purity of the ingredients. 
The source and general preparation of the ingredients have 
already been described. The proportions of the ingredients 
are usually taken as nitre 75 per cent, charcoal 15 per cent, 
and sulphur 10 per cent. 

Nitre, KNOz. This is the oxidizing agent in gunpowder. 
The commercial nitre is always carefully refined before incor- 
poration with the other ingredients. The great difference of 
solubility of nitre in hot and cold water is made use of in 
this refining. The impure salt is dissolved in hot water, the 
solution filtered to remove insoluble matter and allowed to 
cool under continual agitation. The nitre solidifies in minute 
crystals during the cooling and gives saltpeter flour. This 
flour is subjected to two or three washings in small quantities 
of water insufficient to dissolve it, to remove adhering liquid 
and then drained, when it is ready for incorporation. 

The nitre for gunpowder should give no cloudiness in 
solution with a soluble salt of silver or of barium. 

Sulphur. The crude sulphur of commerce is refined by 
distillation and the distilled sulphur is the variety used in the 
manufacture of gunpowder. It has been pointed out that the 
distilled sulphur belongs to the soluble or electro-negative 
variety while the sublimed sulphur belongs to the electro- 
positive variety. The first belongs to the same electro- 
chemical group as oxygen and it is conceivable that this 
fact may explain the difference in properties of the two 
varieties. It is generally thought that the sublimed sulphur 
from its mode of deposition may contain acid vapors in its 
interstices which would act detrimentally. 

The sulphur for powder should burn without residue and 
water in which it has been steeped or agitated should not 
show distinct acid properties. 

Sulphur lowers the igniting point of powder, accelerates 



326 

the combustion, increases the temperature of combustion, 
and the volume of gases evolved. It also gives permanent 
solidity to the grain and prevents crumbling to dust. 

Charcoal. This is the principle combustible of the pow- 
der. By its oxidation are produced the gases carbon mon- 
oxide and carbon dioxide, with great evolution of heat. The 
charcoals employed result from the destructive distillation of 
several kinds of wood, all of which belong to the light woods 
as alder, dogwood, and willow. 

The temperature at which the distillation is accomplished 
affects the quality of charcoal. The higher the temperature 
the more nearly pure the charcoal. In general it may be 
said that black charcoal results from temperatures above 
340° C; red from temperatures between 300° and 340° C; 
and brown below 300° C. 

The higher the temperature at which the charcoal is pro- 
duced the less easily it ignites but the combustion is more 
rapid after ignition. 

In some powders the percentage of the constituents is 
different from that given above. The cocoa powder contains 
more nitre and less sulphur. The Duponts in this country 
have made a brown powder in which the sulphur is less, the 
nitre more than that given, and a carbohydrate is used to 
replace some of the charcoal. 

Many attempts have been made to replace potassium 
nitrate in black powder, but it has not been successfully 
accomplished. Sodium, ammonium, and barium nitrates 
have all been tried, but the first two are deliquescent and the 
last is too expensive. In the brown cocoa powder the 
carbon is obtained from rye straw. 

The effects of powder when fired in guns depend both upon 
the composition and the physical texture and structure of the 
powder. These are all varied to meet the demands of the 
military service, and the discussion of these subjects does 
not pertain especially to chemistry. 



327 

Products from the Explosion of Gunpowder. The pro- 
ducts from the explosion of powder vary with the conditions 
under which the explosion occurs. In general it may be said 
that the oxygen of the nitre combines with the carbon pro- 
ducing* carbon monoxide and carbon dioxide. A part of the 
carbon dioxide combines with the potassium forming potas- 
sium carbonate. The sulphur is mainly converted into 
potassium sulphate. The nitrogen present in the powder is 
liberated. The nitrogen, the carbon monoxide, and the 
carbon dioxide expanded by the heat of the oxidation ac- 
count for the explosive effect. The formula usually assumed 
to represent the general results of the explosion is 4KN0 3 + 
C 4 +S=K 2 C0 3 +K 2 S0 4 +N 4 +2C0 2 +CO. 

Besides the products indicated there are always others 
present in small quantity. From the above formula by the 
consideration of molecular weights, it is seen that solids 
constitute nearly two-thirds by weight of the products of 
explosion and the gases a little over one-third. With brown, 
slow-burning powders the proportion of solids is less and 
that of gases more. The smoke from gunpowder is due to 
the solid constituents. 

G-unpowder explodes at 316° C. It can be exploded by 
percussion. 

Chlorate Mixtures. A large number of chlorate mixtures 
has been invented but none of them has found general 
application as powder. They are mainly used in pyrotechny 
and as fuse mixtures. 

EXPLOSIVE COMPOUNDS. 

It has already been stated that a simple explosive com- 
pound is composed of a single substance. Other explosive 
compounds are composed of more than one substance ami 
while they are not definite chemical compounds their in- 
gredients can not be separated by purely mechanical means 
as in the case of explosive mixtures. 



328 

The most important bodies which are classed as explosive 
compounds are the nitro-explosives or those explosives as- 
sociated with other substances or with each other. In the 
nitro-explosives there is present as a constituent in the mole- 
cules an N0 2 group which supplies the oxygen involved in 
the chemical transformations of the explosive. This N0 2 
group is introduced into the explosive by the action of nitric 
acid upon a hydrocarbon or a hydrocarbon derivative. 

The most important of the nitro-explosives are the nitro- 
compounds and the organic nitrates. The most important 
group of the nitro-compounds are those resulting from the 
action of nitric acid upon the benzene hydrocarbons. Nitro- 
glycerine and gun-cotton are the most important examples 
of organic nitrates. Gun-cotton was formerly thought to be 
a nitro-substitution compound but it is now classed among 
the organic nitrates. Nitro-glycerine is an ethereal salt of 
nitric acid. 

All these classes are produced by the action of nitric acid 
upon hydrocarbon derivatives and in each case the resulting 
molecular change consists in the substitution of one or more 
groups of XO2 for one or more atoms of hydrogen in the 
derivative. The precise distinction between substitution 
compounds and organic salts will be stated after we have 
described some of the bodies. We may without any incon- 
venience consider the classes named as derived by the re- 
placement of one or more hydrogen atoms by one or more 
groups of N0 2 . We shall first describe the two principal 
organic nitrates and some of their derivatives. 

XITEO-GLYCEEIXE OE XITEIC GLYCEEIDE. 

Nitro-glycerine is prepared by the action of a mixture of 
strong nitric and sulphuric acids upon glycerine. The func- 
tion of the sulphuric acid seems to be to preserve the 
strength of the nitric acid by combining with the water 
liberated during the transformation of the glycerine. The 



329 

reaction for the conversion is represented by C 3 H 5 (OH) 3 + 
3HN0 3 =C 3 H 5 (N0 3 ) 3 +3I1 2 (). It is prepared by gradually 
adding* glycerine to a mixture of strong nitric and sulphuric 
acids, the best proportions being three of nitric to five of 
sulphuric by weight, both acids being of great strength. 

Properties of Nitro-glycerine. Nitro-glycerine is a heavy 
oily liquid of specific gravity 1.6 at 15° C. When pure it is 
white, without odor, but the commercial product is usually 
pale yellow. It is poisonous when taken internally. It is 
insoluble in water, soluble in ether, benzene and methyl- 
alcohol; it is less soluble in ethyl- than in methyl-alcohol. 
When pure it has been kept ten years without deterioration. 
It solidifies at about 8° C. though the freezing point varies 
with the quality of the nitro-glycerine. In the solid form it 
is much less sensitive than in the liquid state. 

It explodes by concussion. If a small quantity of it be 
ignited it will burn away without explosion. In a confined 
space it explodes when heated up to 180° C, though in small 
quantity it has been heated to a higher temperature without 
explosion. Nitro-glycerine which has not been thoroughly 
freed from acids or when subjected to too high a temperature 
is liable to become dangerous from spontaneous decomposi- 
tion. It is exploded by detonation through mercuric fulmin- 
ate. It will undergo the sympathetic detonation referred to 
by means of gun-cotton. 

The products of the explosion of nitro-glycerine are shown 
by the reaction, 2C 3 H 5 (N0 3 ) 3 (exploded) =5H 8 0+6C0 2 +0+ 
6N. The temperature of combustion or calorific intensity of 
nitro-glycerine, that is the temperature to which its heat 
of combustion would raise the products, is 3005° 0. accord- 
ing to Vuick. The gaseous products from the explosion of 
nitro-glycerine are about 1500 times the volume of the ex- 
plosive taken at 15° C, the gases being measured at the tem- 
perature of 100° C. and under atmospheric pressure. 

Owing to the dangerous nature of liquid nitro-glycerine 



330 

its use in this form has long since been abandoned in Europe 
and it is now not generally used in this country. 

Nitro-glycerine Derivatives. To overcome the objections 
to the fluid form many explosives of which this is the basis 
have been tried. These derivatives of nitroglycerine may 
be grouped into two classes, 1st, When nitro-glycerine is 
associated with a chemically inert substance, and 2nd, When 
with a substance that takes chemical part in the explosion. 

The most important of the first group is common dyna- 
mite, usually termed dynamite No. 1. It consists of nitro- 
glycerine absorbed by a porous siliceous earth which is 
mainly composed of the shells of diatomacese. The better 
forms of this earth will absorb three times their weights of 
nitro-glycerine. The earth only serves to give solid form to 
the explosive. 

To the second class belongs a large number of explosives 
consisting of nitro-glycerine associated with chemically active 
substances. Charcoal and charred sawdust are used to absorb 
it and it is mixed with gunpowder and other nitrate and 
chlorate mixtures. Nitro-glycjine is also mixed with other 
nitro-explosives some of which will be mentioned later. 

The objects aimed at in associating other substances with 
nitro-glycerine are to get it in less dangerous form than the 
liquid and at the same time to increase its effect by using as 
auxiliary substances bodies capable of combining with free 
oxygen seen to be present in the gases from the explosion of 
nitro-glycerine alone. 

GUN-COTTON, PYEOXYLIN. 

This body is the nitrate of cellulose and results from the 
action of strong nitric acid upon cellulose. The N0 2 groups 
of the acid replace the corresponding number of hydrogen 
atoms in the cellulose. We have given the formula of cellu- 
lose as (C 6 Hio0 5 )n which may be written (C 6 Hio0 5 )2 or 
C12H20O10. Using this formula the reaction for the production 



331 

of gun-cotton is C 12 H 14 4 (OH) 6 +6(HO,N0 2 )=C 12 H 14 4 (0,N0 2 ), 
+6H 2 0. Gun-cotton is a hexanitrate, six atoms of hydrogen 
being replaced by six N0 2 . The formula Ci 2 Hi 4 4 (0,N0 2 ) 6 
may be written 2C 6 H 7 05(N0 2 )3, not forgetting its actual for- 
mula is a hexanitrate ; its production for convenience may be 
represented thus C 6 H 10 O 5 +3(HO,NO 2 )=C 6 H 7 O5 (N0 2 ) 3 +3H 2 0, 
making it similar to that for the production of nitro-glycerine. 

Gun-cotton like nitro-glycerine is prepared by the action 
of a cold mixture of strong nitric acid and sulphuric acid 
upon cellulose. The sulphuric acid serves the same purpose 
as in the manufacture of nitro-glycerine. The cotton is 
perfectly freed from all grease and oil. It is next opened 
up by carding and cutting into short fibres. It is then ready 
for treatment with the acids, after which it has to be thor- 
oughly washed to remove the acid. After washing, the cotton 
is now generally converted into a pulp by a machine similar 
to a rag-engine in a paper mill. It is then subjected to a 
final washing to remove every trace of the acid, drained and 
moulded into blocks, discs, and other forms that may be 
required. The gun-cotton is now seldom employed in the 
form of cotton wool. 

From the chemical change indicated in the reaction it 
is seen that the cotton increases greatly in weight. In 
England from motives of economy, cotton waste is the 
material used for the conversion into gun-cotton. 

Properties of Gun-cotton. Gun-cotton wool can not be 
distinguished from the raw cotton by the eye. It is harsher 
to the touch. It dissolves in acetic ether and acetone. If 
ignited when loose in the air, it flashes with a yellow flame. 
It can be exploded by a blow but generally only the particles 
struck explode. Fully nitrated cotton has often been heated 
rapidly to 180° C. without explosion but it is very risky to 
heat it above 175° C. and it often explodes below this. 

Ignited in a confined space the burning of the first portion 
raises the remainder to the temperature of explosion. Either 



332 

the dry or wet cotton may be detonated by fulminate. Both 
nitro-glycerine and gun-cotton will undergo sympathetic 
detonation, that is, the detonation can be communicated 
along a row of cartridges of either of these explosives, 
though not in contact, when one of them is exploded. Gun- 
cotton like nitroglycerine may be detonated under water. 

The products of the explosion of gun-cotton vary some- 
what with the conditions of the explosion but when perfectly 
detonated they may be expressed by the reaction 2C 6 H 7 5 
(N0 2 )3=7H 2 0+3C0 2 +9CO+6N, which shows that it does not 
contain sufficient oxygen for the complete combustion of the 
carbon. All the products being gaseous as in nitro-glycerine 
there is no smoke. In mining operations the absence of 
smoke is advantageous but the effects of the carbon mon- 
oxide produced are detrimental. By associating the gun- 
cotton with some oxidizing agent the effect of the explosion 
may be increased and the carbon monoxide converted into 
carbon dioxide, thus for many purposes some nitrate is often 
associated with the gun-cotton. 

Collodion Cotton; Soluble Pyroxylin. The common gun- 
cotton just described is a hexanitrate and is insoluble in a 
mixture of alcohol and ether.' The collodion cotton is a 
mixture of several lower nitrates and is soluble in the alcoho] 
and ether mixture. It is made by the action of weaker nitric 
and sulphuric acids upon the cotton. It is less explosive 
than gun-cotton but is largely manufactured for preparation 
of celluloid, smokeless powder, and gelatine explosives. 

Gelatine Explosives. It has been seen that gun-cotton 
contains too little oxygen for the complete combustion of its 
carbon. As collodion cotton is composed of lower nitrates it 
contains still less in proportion to the carbon. The de- 
ficiency of the oxygen in the gun-cotton can be supplied by 
associating it with other substances and this is done in the 
gelatine explosives. 



333 

The simplest and one of the most important of the gela- 
tine explosives is blasting gelatine. This consists of abont 
seven parts of collodion cotton dissolved in about ninety- 
three parts of nitro-glycerine. The excess of oxygen in the 
latter supplies the deficiency of that element in the former. 
This explosive is more powerful than either of its con- 
stituents. Its sensitiveness may be increased by the addition 
of a little gun-cotton and decreased by the addition of a little 
camphor. 

Blasting gelatine is an amber-colored soft elastic mass, 
which can be bent without permanently losing its shape. 

Gelatine Dynamite. To diminish the violence of blasting 
gelatine, it is sometimes thickened with other ingredients, 
the nitro-glycerine in the gelatine being diminished. G-ela- 
tine dynamite and gelignite consist of the same ingredients 
as blasting gelatine in different proportions, incorporated 
with potassium nitrate and wood-pulp. 

Celluloid. This substance is not classed as an explosive 
though masses of it have been known to explode. It is 
composed of collodion cotton and a large percentage of 
camphor. The proportions usually employed are two parts 
of collodion cotton and one part of camphor. Celluloid appears 
to be a mechanical mixture, the camphor being capable of 
extraction by proper solvents. Celluloid is generally made 
from tissue paper. 

Xylonite and artificial ivory are forms of celluloid. 

NITRO-EXPLOSIVES FEOM THE BENZENE GROUP. 

Nitro-compounds. As already stated the nitro-explosives 
from the benzene derivatives are nitro-substitution com- 
pounds as distinguished from organic nitrates. The distinc- 
tion between the two classes will be referred to later, but as 
stated, for our purposes both classes may be assumed to be 
formed the same way, that is by the replacement of one or 



334 

more atoms of hydrogen in the hydrocarbon by one or more 
groups of X0 2 . 

Nitrocompounds of Benzene. By the action of nitric 
acid upon benzene three nitro-benzenes may be produced, 
mono-, di-, and tri-nitro-benzenes, C 6 H 5 X0 2 , C 6 H 4 (NQ_) 2 , and 
C 6 H 3 (X0 2 ) 3 . The first two are not explosive in themselves 
but are associated with other substances in the preparation 
of certain explosives. Tri-nitro-benzene is said to be explo- 
sive though it has not yet been used as such. The nitro- 
benzenes need not therefore be here considered as explosives. 
Mono-nitro-benzene is largely used to prepare aniline, from 
which is obtained a host of beautiful dyes. 

Tri-nitro-pkenol; Picric Acid. This is an important nitro- 
compound from the benzene derivative phenol. It is ob- 
tained by the nitration of phenol, carbolic acid, C 6 H 5 OH. 

The action of nitric acid upon phenol may be represented 
by the equation, C 6 H 5 OH+3(HO,X0 2 ) =C 6 H 2 (X0 2 ) 3 OH+3H 2 0. 

Picric acid is explosive and is used to a limited extent as 
such, but the acid is far more important because of the salts 
it produces which are more stable than the acid and very 
explosive. 

It may be said that the nitro-compounds from the ben- 
zene group are not in general explosive and are not used 
alone but they are all used as auxiliaries in the preparation 
of explosives. It will only be possible to mention a few of 
the important examples. 

Rack-a-Rock the explosive used in the great explosion at Flood 
Eoek (Hell Gate), New York, consisted of mono-nitro-benzene absorbed 
by potassium chlorate. 

Bellite. This is a mixture of ammonium nitrate and di-nitro- 
benzene. 

Several military powders hare been made which consist of mix- 
tures of ammonium and potassium picrates with nitre or with nitre 
and charcoal. 

Xitro -co in pounds and Organic Nitrates. The distinction between 
anitro-compound or substitution product and a nitro-ether or ethereal 



335 

salt is based upon the transformations they undergo when subjected to 
the action of certain reagents. From this basis the N0 2 group which 
is present in both classes is believed to be differently attached in the 
molecule. Some of the nitro-compounds have the same molecular for- 
mulae as certain nitro-ethers but they are found to be metameric bodies 
and not isomeric; thus the ether salt, C 2 H 5 ONO, (ethyl nitrite) is 
metameric with the substitution compound nitro-ethane C 2 H 5 N0 2 . 
The reactions which the two classes undergo justify the belief that the 
hydrocarbon radical is connected to the nitroxyl group through the N 
atom in the substitution compound and through an O atom in the 
ethereal salt. There is also reason for thinking that the mode of for- 
mation of the two classes is different. This difference can be better 
understood by an illustration. The nitro-compound C e H 5 N0 2 (nitro- 
benzene) may be considered as produced by the action, C 6 H 5 ,H(ben- 
zene)+HO,N0 2 =C 6 H 5 N0 2 --|-H 2 0, in which either the N0 2 replaces the 
H of the benzene or the C 6 H 5 replaces the OH of the acid. Nitro- 
glycerine, the nitric ether of glycerine, is an ethereal salt of nitric acid 
resulting from the replacement of the hydrogen of the acid by the basic 
alcohol radical of glycerine, C 3 H 5 (OH)3+3(OH,N0 2 )=C 3 H 5 (0,N0 2 )3+ 
3H 2 0. In this the trivalent radical C 3 H 5 replaces three atoms of 
hydrogen, or the acid radical N0 2 replaces the hydroxyl hydrogen of 
the alcohol. Considering the hydrocarbon radical in the two cases, 
it is seen that in nitro-benzene the radical has replaced OH, in the 
nitro-glycerine it has replaced H. All ethereal salts may be considered 
as formed in this way, by the replacement of the hydrogen in the acid 
by the alcohol radicals. 

These ethereal salts are also called esters and the distinction 
between the constitutional formulae of these and nitro-compounds may 
be generally represented by R-— NO, and R— O— N0 2 , in which R stands 
for a hydrocarbon radical, the N atoms being directly connected with 
the radical in the compounds and through O atoms in the ethers. 

Gun-cotton was formerly classed as a nitro-compound but it is now 
thought to be an organic nitrate, cellulose nitrate. This conclusion is 
reached from the fact that under the action of reagents its reduction 
products place it among the organic nitrates rather than among the 
nitro-substitution compounds. 

SMOKELESS POWDEKS. 

It was natural that in the first efforts to prepare a smoke- 
less powder as a propelling agent, it should have been 
attempted to use some of the known high explosives which 
left no solid residue in exploding. Many attempts were made 
to adapt gun-cotton to this purpose as it was thought to 
promise most favorable results. These early attempts were 



all mainly based on a physical manipulation of the cotton 
wool and resulted in failure. 

The smokeless powders of the present day may be grouped 
into three general classes. 1st. Those in which the only 
explosive used is some form of nitro-cotton: 2nd. Those in 
which nitro-glycerine and some form of nitro-cotton are 
used: 3rd. Those in which nitro-derivatives of benzene alone 
or with nitro-cellnlose are used. 

The more important and successful powders belong to the 
first class. 

The first class includes a number of powders made by 
kneading the nitro-cotton in a proper solvent and bringing it 
to such a consistency that it can be rolled into tenaceous 
sheets after which it is cut into flakes. These powders are 
known as flake powders and are largely made in several 
European countries. By a little different manipulation the 
kneaded mass is converted into grains and gives granulated 
powders. The solvents used are acetic ethers or acetones. 
These powders sometimes contain some additional substance 
to retard then action when ignited, but by careful manipula- 
tion they are now made without such addition. The effect 
of the solvent and the physical treatment produce the desired 
result. Some of the powders are glazed which has a retard- 
ing effect upon their explosion. The second class includes a 
number of noted powders made by dissolving collodion cotton 
in nitro-glycerine or gun-cotton in nitro-glycerine and acetone. 

In these powders the ingredients are kneaded or thoroughly 
mixed together and may be then rolled into sheets or cut into 
flakes or may be pressed through small cylindrical openings 
into cords or fibres. Ballistite, cordite, and the American 
Leonard and Peyton powders fall into this class. Each of 
these powders contains a small addition of certain other sub- 
stanses for decreasing rapidity of action. 

The third class includes a number of powders resulting 
from associating picric acid or the picrates with other 



337 
« 

substances, the picrates of potassium and ammonium are 
employed. In indurite invented by Professor Monroe formerly 
of the Naval Torpedo Station, gun-cotton is dissolved in 
nitro-benzene. One of the American smokeless powders by 
the Duponts is also made by dissolving nitro-cellulose in 
benzene. As already stated the last class is of little import- 
ance compared with the other two. 

The number of explosives and powders is entirely too 
great to be here described or even mentioned. The physical 
manipulation involved in their preparation does not properly 
belong here and only their general chemical relations have 
been referred to. 

FULMINATES. 

The fulminates are the salts of fulminic acid. The acid has not 
been isolated but its formula is assumed to be C 2 N 2 2 H 2 . The princi- 
pal salts of this acid are the fulminates of mercury and silver; the 
other metallic fulminates are obtained from these. 

The most important is that of mercury commonly known as ful- 
minating mercury. This fulminate is prepared by dissolving mercury 
in nitric acid and acting- upon it with alcohol, its formula is C 2 N,0 3 Hg. 

It is a, white solid when pure but is usually of a grey color. It is 
extremely sensitive to explosion and detonates by percussion, by heat 
(187° C), by the electric spark, or by contact with nitric or sulphuric- 
acid. Its explosion is represented by the reaction HgC 2 N 2 2 (ex- 
ploded)=Hg+2CO+N 2 . 

It is used mainly to detonate other explosives. For this purpose it 
is employed either singly or with other substances. Potassium chlor- 
ate, nitrate, meal powder, and antimony sulphide are some of the com- 
mon substances used with it. 

The fulminate or the fulminating mixture is enclosed in thin metal- 
lic cylinders for use as detonators. 

It will be observed that mercuric fulminate contains an N0 2 group 
and a hydrocarbon derivative (alcohol) is employed in its preparation 
though it does not contain hydrogen. The rational formula of the 
body has not yet been agreed upon. 

ILLUMINATING GAS. 

COAL GAS. 

The idea of preparing an illuminating gas from coal 
seems to have become first well denned in the mind of 

22 



338 

William Murdoch, a Scotchman, in 1792. In this year he 
lighted his house with coal gas. By the year 1800 he had 
extended the use of the new illuminant to all the principal 
shops and foundries near Birmingham. Murdoch's inven- 
tion did not become known on the continent of Europe until 
the beginning of the nineteenth century. The French claim 
the invention for their countryman Lebon, who in 1801 
illuminated his house with gas from wood. Gas lighting was 
first introduced into the streets of London in 1807 and had 
become general by 1814. Paris was lighted by gas in 1820 
and after this date the use of gas rapidly spread over 
Europe. The manufacture of gas has ever since been an 
industry of great extent and magnitude. The gas generally 
designated as coal gas and used for illuminating purposes is 
a mechanical mixture of a number of permanent gases some 
of which are luminous while others produce little light when 
separately burned. There are also present the vapors of 
many substances which greatly add to the light-giving power 
of the gas. Coal gas is generally manufactured by the 
destructive distillation of bituminous coal. 

Bituminous coal is essentially composed of carbon, hydro- 
gen, oxygen, nitrogen, sulphur, and a little mineral matter. 
In general the carbon amounts to about seventy-five per cent 
of the coal. When bituminous coal is subjected to the action 
of heat out of contact with air, there results a large number 
of compounds composed of two or more elements of the coal. 
There have already been distinguished nearly a hundred 
bodies among the products of the distillation of coal. It is 
evident from this fact that coal is a complex body. The 
original arrangement of the elements in the coal has not 
been determined but it is certain that the numerous distilla- 
tion products are not primary constituents of the coal but 
result from the application of heat. They are products of 
the distillation and not mere educts from the coal. 



339 
COAL GAS MANUFACTUKE. 

Retorts. In the manufacture, bituminous coal is placed 
in fire-clay retorts capable of being hermetically sealed. The 
retorts are generally D shaped cylinders about ten feet long 
and from fourteen to twenty inches in diameter. The charge 
of coal is usually from two hundred to four hundred pounds 
and remains in the retort from four to six hours. The coal 
is always introduced into a heated retort. The retorts are 
arranged in benches so that a number can be heated by the 
same furnace and they are kept above a red heat. During 
the heating the volatile products of the distillation are driven 
off and coke is left in the retorts. 

The principal products of the distillation which pass from 
the retorts are vaporized liquid hydrocarbons, water vapor, 
hydrogen, marsh gas, acetylene, olefiant gas, ammonia, 
hydrogen sulphide, carbon dioxide, carbon monoxide, cyano- 
gen, nitrogen, and carbon disulphide. 

Ascension Pipe and Hydraulic Main. From the front 
upper surface of each retort rises an iron pipe. These pipes 
extend upward and then curve down and enter a large iron 
cylinder called the hydraulic main which runs perpendicular 
to and above the retorts and receives the pipes from all the 
retorts. 

The hydraulic main is kept partially full of water and 
other condensed liquid-products of distillation. The ends of 
the pipes from the retorts dip beneath the liquid in the main. 
A portion of the heavy hydrocarbon vapors are condensed in 
the hydraulic main and nearly all of the aqueous vapor. The 
former constitutes tar and the condensed aqueous vapor 
takes up ammonia, carbon dioxide, hydrogen sulphide, and 
cyanogen forming what is known as the ammoniacal liquor. 

The gases and more volatile products of the distillation 
bubble up through the liquid in the main. This liquid acts 
as a seal to prevent the gases from returning to the a spon- 
sion pipes when the retorts are open for recharging. 



340 

Condensers. From the hydraulic main the uncondensed 
products are carried by an iron pipe called the foal main 
to the condensers. The condensers are a series of pipes 
through which the gas passes and which furnish a large cool- 
ing surface ; the condensers may be cooled by running water 
or simply by exposure to the air. In the condensers are 
deposited the liquid hydrocarbons (tar), ammoniacal salts, 
and aqueous vapor which have passed through the hydraulic 
main. The condensed products are conducted by pipes to 
suitable receptacles for removal. 

Exhausters. Immediately after the condensers exhausters 
are usually placed. The exhauster is a form of pump for 
pulling the gas away from the retort and forcing it through 
the subsequent parts of the plant into the holder. If it were 
not for the exhauster the pressure of the gas in the retorts 
would have to be sufficient to overcome all the resistances in 
the different parts of the plant and thus cause loss of gas by 
leakage in the retorts. 

Washers and Scrubbers. From the exhausters the gas 
passes through the washers and scrubbers or through scrub- 
bers alone. The washers are arrangements in which the gas is 
made to traverse thin layers of liquid. In scrubbers the gas is 
not forced to pass through the water but is brought into inti- 
mate contact with wetted surfaces . A common form of scrubber 
is a cylinder filled with coke over which water continually 
trickles. In the passage through the washers and scrubbers 
the remaining ammonia and some of the hydrogen sulphide 
and carbon dioxide are removed. 

Purifiers. From the scrubbers the gas passes through 
the purifiers, the object of which is to remove the remaining 
hydrogen sulphide from the gas. The purifiers are generally 
square iron boxes, divided by a number of horizontal sieves. 
The purifying material is placed in layers upon these sieves 






i 




J 











I- 38 ! 






341 

and the gas is made to traverse the several layers before 
leaving the purifiers. 

The materials used in the purifiers are slaked lime or iron 
oxide either separately or in succession. The slaked lime 
takes out both hydrogen sulphide and carbon dioxide while 
the iron oxide removes only the hydrogen sulphide. The 
carbon dioxide diminishes the illuminating power of the gas 
and when not removed the illuminating power can only be 
kept up by enriching the gas in a manner yet to be 
explained. 

The great advantage of the iron oxide is that its purifying 
power can be restored a number of times by simply exposing 
it to the atmosphere. The lime can not be used again and 
can not be economically used except where it is very cheap 
and can be readily disposed of when spent. If the substances 
are used in succession it is better to pass the gas through the 
iron oxide first and then through the lime. When lime is 
employed as the purifying agent calcium sulphide and 
calcium carbonate are produced ; when iron oxide is employed 
the mono- and sesqui-sulphides of iron are produced. When 
these sulphides are exposed to the air the iron oxide is repro- 
duced and the sulphur deposited. The oxide may thus be 
repeatedly revivified until the separated sulphur amounts to 
55 per cent. Purification by iron oxide is the method now 
generally employed. 

The reactions in the iron purifiers are Fe 2 3 -f 3H 2 S = 
Fe 2 S 3 +3H 2 0; ' Fe 2 3 +3H 2 S=2FeS+S+3H 2 0. The oxide is 
reproduced by exposure to the air and the reactions are 
2FeS+0 3 =Fe a 3 +S 8 and Fe 2 S 3 +0 3 =Fe 2 3 +3S. The oxide 
of iron used may be a natural product, bog iron ore, or it 
may be artificially prepared by the oxidation of iron borings 
or filings. In this country the oxide is very generally pre- 
pared in the manner mentioned. 

The carbon disulphide is one of the most difficult im- 
purities to remove from the gas when it is there present, and 



342 

there is demanded for this result special provision not 
deemed necessary for description here. 

The Gasometers. From the purifiers the gas passes to 
the holders or gasometers and is stored for use, and dis- 
tributed as required to consumers. 

The composition of purified coal gas differs at different 
places, in general it may be stated that the composition is 
approximately H=50 per cent: saturated hydrocarbons of 
the paraffin series mainly marsh gas =30 to 40 per cent; un- 
saturated hydrocarbons, mainly benzene, acetylene, and 
ethene, 3 to 5 per cent; nitrogen, 3 to 5 per cent; carbon 
monoxide, 3 to 5 per cent, with small quantities of oxygen 
and carbon dioxide. 

The luminosity of the gas is believed to be due to the 
combined action of the hydrocarbons and can not in a great 
degree be attributed to any one of them alone. The quality 
of the gas is of course affected by the temperature of the 
distillation. At too low a temperature the solid and liquid 
hydrocarbons are too abundant, at too high a temperature 
the gaseous hydrocarbons are decomposed, carbon being 
deposited as gas carbon and hydrogen being liberated. 

The illuminating power of gas from common coal was 
formerly l^eq uefiUy ^ increased by adding to the charge of the 
retort a small quantity of cannel coal. This result is now 
frequently brought about by impregnating the gas with 
vapor of the volatile hydrocarbons. This is often done in 
this country by introducing into the retort a small iron 
cylinder (called cartridge) containing paraffin oil obtained 
from petroleum. 

Secondary Products from Coal Gas Manufacture. The 

secondary products from the gas manufacture are numerous 
and important. The hydraulic main, the condensers, and 
the scrubber constitute the source of nearly all the am- 
moniacal salts of commerce. The coal tar by distillation 



343 

readily yields two portions, the light and heavy oil. From 
the light oil naphtha, benzine, toluene, and other less im- 
portant bodies are obtained ; from the heavy oil naphthalene 
and carbolic acid are obtained. Besides the bodies named 
there are many others of great theoretical importance to 
organic chemistry. 

ALCOHOLIC BEVERAGES. 

The different alcoholic beverages of mankind may be 
grouped into two classes — 1st, fermented, 2nd, distilled. The 
fermented may be divided into the less general classes, leers 
and wines. These classes with the general principles of their 
production will be briefly described. 

Fermented Liquors; Beers and Wines. Beers are the 
products of fermentation of glucose which has been directly 
produced by the transformation of starchy substances. 
Wines are the products of the fermentation of glucose exist- 
ing as such in the fruits used. 

BEER-MAKING. 

Malting. Beer is generally produced from barley. In 
the operation of malting, the grain is first soaked in water 
until it has swollen and become soft. It is then spread in 
layers, under the proper condition for germination, in a 
dark place kept at a constant and moderate temperature. 
Under these conditions the grain sprouts and when the 
radicle or sprout has grown to about half an inch, the 
vitality of the grain is destroyed by kiln-drying and the 
radicle made brittle by the final temperature, to which it is 
subjected so that it is easily broken off and can be removed 
by sifting. The radicle is valuable as a manure as it contains 
about one-ninth the nitrogen of the grain. 

During the germination the seed absorbs oxygen and 
gives off carbon dioxide and there is produced a Substance 
known as diastase which converts some of the starch into 



344 

dextrin and glucose, which then serve as food for the de- 
veloping radicle. Diastase contains carbon, hydrogen, oxy- 
gen and nitrogen but its formula is not known. The malted 
grain contains about one-fifth per cent of its weight of 
diastase. 

Brewing. Preliminary to brewing the malted grain is 
ground to an even grist and infused in water at the tempera- 
ture of about 77 = C. when it is left for several hours, during 
which the diastase acts upon the unaltered starch and con- 
verts the greater portion of it into sugar and dextrin. The 
water with its dissolved constituents is called wort. It is 
drawn off from the exhausted malt and run into a wort- 
boiler. The exhausted malt contains some starch and nitro- 
genous matter and is used as food for animals. 

The wort is next boiled with the requisite quantity of 
hops. The flowers of hops contain a bitter principle called 
lupulin and an essential oil. They confer upon the beer 
its aromatic flavor and odor and tend to prevent the con- 
version of the alcohol into acetic acid. The boiling also 
effects the removal of a considerable quantity of nitro- 
genous matter resulting from the gluten of the grain, which 
matter would be deleterious upon the keeping properties. 

After boiling with the hops the wort is drawn off and 
cooled rapidly to about 15° C. to avoid the action of the air 
in producing acid fermentation, if cooled slowly. The wort 
is then transferred to the fermenting vessels or tuns and 
made to ferment by the addition of the proper quantity of 
yeast. 

Yeast is a vegetable micro-organism (already referred to) 
which possesses the power of converting sugar into alcohol 
and carbon dioxide. It is also capable of inducing the con- 
version of cane sugar into glucose. 

The fermentation is the most important part of the opera- 
tion of brewing. The process is controlled by attention to 
the temperature of the liquid and the general appearance of 



345 

the tuns. The extent to which the fermentation has pro- 
ceeded can be well determined by the density of the wort. 
The yeast is always removed before the fermentation is com- 
pleted and the beer drawn off into casks where it undergoes 
a slow fermentation and then becomes charged with carbon 
dioxide. 

The finished beer besides the water, alcohol and carbon 
dioxide, contains some unchanged glucose and dextrin, the 
extract from the hop, some nitrogenous matter from the 
grain, and the soluble mineral matter of the grain except the 
phosphates, which are consumed by the yeast. There are 
present in small quantity other secondary products of the 
fermentation as acetic acid, glycerin, etc. 

Porter, stout, and highly colored beer are made by 
having a small quantity of the malt strongly dried or charred 
so as to convert some of the sugar into caramel. The amount 
of alcohol in beers varies from two to nine per cent. 

The beer yeast if deprived of moisture by drying at a low 
temperature or by pressure can be kept for a long time with- 
out losing its powers but if heated to 100° C. it is killed and 
is no longer capable of producing fermentation. 

The yeast plant grows and increases at the expense of the 
phosphates and nitrogenous matter of the wort, these being 
necessary to its growth. As previously stated it is during 
the growth of the yeast that fermentation takes place. In a 
solution of pure sugar the yeast will transform only a limited 
quantity of the sugar and is destroyed by the action. 

WINE-MAKING. 

We have stated that the wines result from the fermenta- 
tion of the glucose existing in the fruits from which the wine 
is made. The term is generally applied only to those 
beverages made from grapes. Wine further differs from boor 
in that the maker adds no ferment. The expressed juice of 
the grape undergoes spontaneous fermentation. This fer- 
mentation is due to the fact that the yeast spores are! gen- 



346 

erally present on the skin and stalks of the grape and are 
carried about by the air. The grape juice contains the 
necessary constituents for the sustenance of the yeast, and 
when the yeast spores are deposited in it they readily grow, 
with the resulting vinous fermentation. If all the sugar be 
fermented the wines are said to be dry, otherwise the wine 
remains sweet. 

The skins, stalks, and seeds of the grape contain tannic 
acid with several coloring matters. The color and slightly 
astringent taste of the red wines are due to the fact that the 
skins are left for a certain time in the fermenting juice and 
the alcohol produced, dissolves out the tannic acid and the 
coloring matter. In white wine the fermentation does not 
take place in contact with the skins. Red wines are generally 
fermented in vats, white wines in casks. 

After fermentation the wines are decanted and very fre- 
quently clarified in addition. Eed wines are usually clarified 
by albumen, while the white are clarified by gelatin (isin- 
glass). The action of the albumen or gelatin is purely 
mechanical. The tannin in the wine acts upon these bodies 
forming a precipitate which carries with it any suspended 
impurities of the wine. The great amount of tannin in the 
red wines permits the use of albumen, while isinglass is used 
with white wines. 

Acid potassium tartrate is present in considerable quantity 
in the grape juice. The solubility of the salt decreases with 
the increase of alcohol so that the slight fermentation which 
goes on after the bottling or casking causes a deposition of 
the salt. With the removal of the tartrate the coloring mat- 
ter becomes less soluble and falls giving the wine a lighter 
color. 

In effervescent wines the fermentation is continued after 
bottling, and the carbon dioxide liberated under pressure, is 
retained in the liquid. Champagne is the most important 
effervescing wine. Its manufacture requires great care and 



347 

skill hence the wine is very expensive. For champagne the 
must or grape juice is very carefully clarified and the wine 
bottled before the fermentation has entirely ceased, sugar 
being added at the same time, as there is not enough left in 
the wine to continue the fermentation to the desired point. 
After fermenting for a time in the bottles the corks are 
removed and the compressed gas discharges the yeast and 
other impurities. The bottles are then refilled with a specially 
prepared white wine or liquej, recorked, and sealed for the 
market. The different processes require six or seven months 
and during the fermentation in the bottles there is much loss 
due to breakage. In the dry est champagnes the pressure of 
the gas often reaches five or six atmospheres. 

In the manufacture of red wines it was formerly the cus- 
tom in wine-making countries, and still is in some places, to 
crush the grapes by the bare feet of men treading upon 
them. This crushing is the preliminary to the pressing of 
the grapes. In the making of champagne the grapes are not 
crushed before being put into the presses, the only crushing- 
being by the press; this gives a, purer juice. 

The reason that the grape is superior to all other fruits 
for wine-making is that its vegetable salt is potassium tartrate 
which as above explained is deposited as the alcohol in- 
creases and the sugar disappears. Wine made from goose- 
berries, currants, apples, etc., contains malic and citric acids 
which can not be thus removed and consequently their 
acidity must be overcome by the addition of sugar. 

Cider is a wine which results from the fermentation of the 
fruit sugar of the apple. It may contain from seven to ten 
per cent of alcohol. 

A solution containing more than one-third its weight of 
sugar will not undergo vinous fermentation and when the 
alcohol produced amounts to about seventeen per cent of the 
solution the fermentation ceases. This limit fixes the max- 
imum strength of fern urn ted liquors. 



348 
DISTILLED LIQUORS. 

The stronger alcoholic beverages of mankind result from 
the distillation of fermented liquors. They may be brought 
into two general classes, whiskies and brandies. 

Brandies. These result from the distillation of wines. 
The brandy from^wmes is considered the best. In this 
country a brandy is made from apple cider and one from the 
juice of the peach. 

Whiskey. Whiskey is made by distilling the fermented 
products of various starchy substances. Those generally 
used are Indian corn (maize), rye, barley, rice, and oats. In 
this country whiskey is made in large quantity, corn and rye 
being the principal grains employed. That from corn is 
generally known as Bourbon whiskey. 

The grain is malted quite similarly as for beer, but as the 
diastase for the. malt is far greater than necessary to convert 
its sugar into al^nSt - distillers generally add a large portion 
of unmalted grain whose starch is also converted. The 
extract from the grain is fermented as in beer-making and as 
the distiller endeavors to produce as much alcohol as pos- 
sible the fermentation is urged to its utmost. This fermented 
liquor is then subjected to distillation, the portion passing 
over during the process constituting the whiskey, the re- 
siduary liquid being of little value. The alcoholic strengths 
of both fermented and distilled liquors vary between wide 
limits and there is such a large number of each kind that it 
is impracticable to give detailed descriptions. The genuine 
wines, whiskies, and brandies are to a considerable extent 
now imitated by mixing liquors of different strengths and 
adding certain flavoring and coloring materials. 

BREAD=MAKINQ. 

The essential constituents of bread-making grains are 
water, starch, nitrogenous matter, dextrin, cellulose, a little 



349 

sugar and some fat, and inorganic salts. The nitrogenous 
matter is mainly in the form of gluten and albumin. The 
gluten is composed of vegetable fibrin, of a substance 
resembling casein and of vegetable glutin. The gluten is 
the most important constituent for bread-making. It is 
because of the tenacity of the wheat gluten that it is supe- 
rior to all other grains for bread-making. This tenacity is 
due to the vegetable glutin or gliadin, it is this compo- 
nent of the gluten that gives adhesiveness to the dough. - 

When wheaten flour is kneaded upon cloth the gluten is 
left as an elastic, tenacious mass. The gluten is the main 
flesh-forming constituent of the flour, but in its natural 
state it is tough and difficult of digestion. In good bread 
the dough is so manipulated that the whole is rendered light 
and porous, thus becoming more palatable and more digesti- 
ble, exposing a large surface to the action of the digestive 
fluids. Eye stands next to wheat as a bread-making grain, 
and it is largely used for that purpose in northern Europe. 
Wheat is the chief bread-making grain. 

The essential and desired qualities of lightness and poros- 
ity are conferred upon bread by incorporating with the 
dough, carbon dioxide under pressure. The tenacity of the 
gluten prevents the ready escape of the gas and as it 
expands the required texture is produced in the dough. 
This vesiculated texture is made permanent in the bread 
by the solidification which results from baking. 

The carbon dioxide employed may be produced by fer- 
mentation within the dough or is otherwise introduced therein. 
In the former case fermented bread results, in the latter 
unfermented. 

Fermented Bread. In this kind of bread various kinds of 
yeast are employed, the result being a vinous fermentation 
by which the sugar of the dough is converted into carbon 
dioxide and alcohol. These escaping through the gluten 
cause the dough to rise. A little yeast incorporated with 



350 

some dough is placed in a suitable temperature. When this 
charge has worked a while it is kneaded with the remaining 
batch of dough. The fermentation then pervades the whole 
and after a short interval the loaves are formed and placed 
in the oven. 

Sometimes leaven is employed to bring about fermenta- 
tion. Leavening has been practiced from remote ages. It 
consists in placing a small quantity of dough under favor- 
able conditions to undergo natural fermentation, and when 
this has set in. the leaven is mixed with the dough and the 
whole undergoes fermentation. In this case the cause of the 
fermentation is minute organisms introduced into the dough 
from the air. 

In fermented bread the sugar which is fermented is that 
present in the grain and it is also partly derived from the con- 
version of starch into sugar. It is seen that vinous fermenta- 
tion plays an important part in bread-making. A considerable 
amount of alcohol is given off in the making of such bread, 
and it acts like the carbon dioxide to lighten the bread. 
Efforts have been made to collect and save the alcohol given 
off m the manufacture of fermented bread, but the necessary 
arrangements injured the quality of the bread and were 
abandoned. 

Unfermented Bread. The most direct method of pre- 
paring unfermented bread is illustrated in the making of 
aerated bread. In this process the flour is brought to the 
state of dough by kneading with water charged with carbon 
dioxide. The whole operation is mechanically performed 
in closed vessels. When the mixing is complete an opening 
is made at the lower part of the vessel and the dough is 
forced out by the pressure of the gas. The vesiculation is 
produced by the expansion of the gas, with which the 
dough is thoroughly impregnated. The expansion begins 
when the dough is removed from the vessel and is still 
further increased by the heat of the oven. In this process 



351 

the dough and bread are untouched by the hands of the 
baker until removed from the oven. 

Unfermented bread is also made by the use of certain 
powders, which react upon each other when moistened with 
water and liberate carbon dioxide. The most common of 
these is a mixture of tartaric acid and acid sodium car- 
bonate. If the powders be thoroughly incorporated with 
the flour the gas will be liberated during the kneading 
with water. Another method is to mix the sodium carbon- 
ate with the flour and then knead with slightly acidulated 
water; dilute hydrochloric acid is frequently employed. 
Ammonium carbonate is sometimes used, it being volatile 
at the temperature of baking. 

Flour is injured if it becomes damp or moist, its gluten 
becoming somewhat soluble and less tenaceous. Such flour 
is greatly improved by adding to the water used in making 
the dough, lime water in the proportion of twenty-seven 
pints to one hundred pounds of flour. 

Hard Bread. This kind of bread is made by baking the 
prepared dough without vesiculating material of any sort. 
All the moisture is expelled from such bread and it is much 
more dense than soft bread and keeps far better. It is 
accordingly better for military and naval stores. Other 
grains than wheat and rye can be used for making hard 
bread. 

One hundred pounds of flour will make considerably over 
one hundred pounds of soft bread, depending upon the 
proportion of the crust and this depends upon the size of the 
loaves. Ordinarily the weight of soft bread will exceed the 
weight of flour by about one-third. The weight of hard 
bread is less by about one-seventh. The staleness of bread 
is not due to its becoming dry, as is frequently supposed, but 
results from molecular change. Its freshness can be re- 
stored by rebaking in a closed oven. 

The cereal grains are richer in inorganic 1 salts and fatty 



35* 

matter in and near the husk. As there is frequently some of 
the integument carried away with the husk, it is evident that- 
unbolted flour has some superiority over the bolted. If 
bread supplied the only article of food this difference be- 
tween the flours would be more important. Besides the 
physical condition of bread which makes it more palatable 
and more digestible than dough, other important changes 
are brought about by the baking. The state of nitrogenous 
constituents is altered and made more digestible. The 
starch granules are ruptured and some of it transformed 
into dextrin and sugar both of which are soluble : this latter 
effect is especially noticeable in the crust and in toast. 

THE PREPARATION OF SOAP. 

A fuller account of the fats and fixed oils, than has yet 
been given, will lead to a better understanding of the chemi- 
cal principles of soap-making. 

Fixed Oils; Fats; Glycerides. These are terms applied to 
a large number of analogous bodies found in both plants and 
animals. It is an interesting fact that there should be such 
a striking resemblance in composition and properties between 
bodies from such distinct sources. 

The term fixed oils is generally used for those members of 
the group which are liquid at ordinary temperature and the 
term fats for those that are solid. A fat is a solid fixed oil. 

These bodies are ethereal salts of the fatty acids. The 
basic part of the salt is the alcohol radical C 3 H 5 , They are 
all capable of saponification yielding glycerine and a fatty 
acid. Owing to the above facts the class is very properly 
termed glycerides. Some of the characteristics of the 
glycerides are as follows. 

Composition. They are all composed of carbon, hydrogen 
and oxygen, being very rich in hydrogen and carbon. They 
yield glycerine and a fatty acid by saponification. 



353 

Solubility. They are practically insoluble in water, but 
dissolve in ether, carbon disulphide and mix in all propor- 
tions with essential oils. 

Stability. If the air be excluded they can be preserved 
for a long time. In contact with air some of them absorb 
oxygen and in thin layers become solid. Such of the fixed 
oils are called drying oils. This oxidation may take place 
with considerable elevation of temperature. If the oil ex- 
pose a large surface, as when tow or cotton waste is moist- 
ened with it, spontaneous combustion may result. Other of 
the fixed oils when exposed to the air do not dry up but 
become rancid and ropy. This change is attributed to the 
presence of impurities. Such oils are called non-drying. 
The fixed oils cannot be distilled without decomposition. 
They are unctions to the touch and the more liquid leave a 
permanent stain on paper. 

Some of the more important of these oils and fats are the 
following: Palm, cocoa-nut, castor oil, cotton-seed and olive 
or sweet oil. Hemp, poppy oil and linseed oil are drying oils, 
the last named being much used by painters. Its drying 
powers are increased when it is boiled with certain metallic 
oxides. Such oxides are termed siccatives. The oils just 
named are of vegetable origin. Some of the others ordinarily 
obtained from animal sources are stearin, Palmitin, margarin 
and olein. Butter is mainly composed of Palmitin, stearin and 
olein. Bees-wax is a fat. 

It will be seen that the above characters establish a broad dis- 
tinction between the fixed oils and the essential or volatile oils. 

MANUFACTURE OF SOAP. 

Soap manufacture is an ancient and important industry. 
The remains of a complete soap-making establishment were 
found in the excavations of Pompeii, with soap still perfect 
though made over seventeen hundred years ago. 

It has just been stated that the more important vegetable 

and animal fats and oils are composed of a fatty acid in 
23 



354 

which the hydrogen is replaced by C 3 H 5 , the radical of 
glycerine or propenyl alcohol, the oils and fats being glycer- 
ides. The general significance of the term saponification has 
been given. Soap is here nsed in the ordinary sense. 

The natural fats or glycerides may be represented by the 
formula C3H5FT3, in which (Ft) stands for a complex mole- 
cule of carbon, hydrogen and oxygen. The fatty acid from 
which the glyceride is derived would be represented by FtH. 
A soap may be defined as the salt of a fatty acid in which 
the hydrogen has been replaced by an alkali metal. 

Soaps are made by the action of an alkali upon the 
glycerides (fats) or sometimes upon fatty acids. The al- 
kalies employed are potassa and soda. The action is brought 
about by boiling the fat with the caustic solution and may be 
indicated by the reaction C3H 5 (Ft)3+3NaOH=3NaFt+C 3 H 8 03, 

Soda Soap Glycerine 

or potassium hydroxide may be used instead of sodium 
hydroxide with the resulting production of a potash soap. It 
will be observed that the alkali metal has replaced the basic 
radical C 3 H 5 . Soaps are generally stearates, oleates or 
palmitates of potassium and sodium. 

Soaps containing sodium are generally hard and those 
containing potassium are generally soft, though it is possible 
to produce a soft soda soap and a hard potassium soap. The 
soaps of the alkali metals are soluble, those of other metals 
generally insoluble. 

Soap can be produced from a large number of fats and 
oils, but only a comparatively small number is employed. 
The principal animal fats are tallow, suet, lard, whale, 
seal and fish oils; the vegetable oils commonly used are 
palm, olive, cocoa-nut and cotton seed. Fish oils contain a 
large proportion of olein, a liquid fat, and are generally used 
with potash to form soft soap, especially in Europe. In this 
country the farmers, in the south and south-west, frequently 
make soap for domestic use from kitchen fats and the alkali 
obtained from wood-ashes. 



355 

The alkali used is generally in the form of the hydroxide 
when soaps are made from fats. Certain soaps are made by 
boiling" the alkaline carbonates with free fatty acids obtained 
in other operations. The alkaline hydroxides are prepared 
in enormous quantity for use in soap-making. 

The glycerine formed during saponification may or may 
not be separated from the soap. Castile soap is made from 
olive oil and marine soap from palm oil. Soap may contain 
from 25 to 75 per cent of water. In the high dry regions of 
our western country soaps have been known to lose nearly 
one-half their weight by evaporation of water. 

The subsequent treatment of the soap after removal from 
the boiling vessels depends upon the object desired and is 
very varied. Many different kinds of ingredients are incor- 
porated for the purpose of affecting the color, odor and other 
properties of the soap. 

Cleansing Power of Soap. This property of soap is 
largely due to its alkalinity. Even a neutral soap gives an 
alkaline solution when treated with water, some of the alkali 
separating and leaving a soap with a greater amount of 
fatty acid than previously existed. The excess of alkali 
acts upon the grease or other insoluble matter and often ren- 
ders its removal possible. To increase the detergent power 
of soap substances are often added which act merely 
mechanically, such are sand and silicate of soda. 

MANUFACTURE OF LEATHER. 

The antiquity of this industry is unknown, but it is cer- 
tain that it was practiced by the ancient Egyptians, for 
pieces of leather taken from a mummy and now in the 
British Museum, bear marks showing that it must have 
been made 900 years B.C. It is well known that the Rom- 
ans attained much skill in the preparation and finishing y^\' 
leather and it is thought that the Chinese were acquainted 
with the art from remote ages. On the other hand it is 



356 

strange, when we recall how universally the skins of ani- 
mals are used by savages, that so many of them should have 
remained ignorant of the art of tanning almost up to the 
present time. 

Leather. If the fresh skin of an animal, cleaned and 
divested of hair, fat and other extraneous matter, be im- 
mersed in a dilute solution of tannic acid a chemical com- 
bination ensues and the gelatinous tissue of the skin is 
converted into a non-putrescible substance, impervious to 
and insoluble in water. This is leather. 

TANNING. 

Preparation of Hides; Cleansing. The first step in the 
preparation of leather is the softening and cleaning of the 
hides. This is done by soaking in water, with frequent 
changes, until the skins are pliable. They are then put 
through a kneading process. The length of time that the 
hides must be soaked depends upon the manner of their orig- 
inal curing. The hides from hot dry countries sometimes 
require two or three weeks 7 soaking. 

©epilation. The hair is removed from the cleaned skins 
by soaking them in lime water; the lime saponifies the fat 
around the roots of the hair and loosens them; or the same 
result may be accomplished by what is termed siveating. In 
this process the hides are suspended in pits and kept at a 
uniform temperature (18° C.) and a moist atmosphere until 
they undergo partial decomposition. The ammonia pro- 
duced acts in the same way as the lime. The sweating 
process is almost exclusively followed in this country in the 
treatment of dried hides. The time necessary in this opera- 
tion varies with the character of the hides treated so that no 
particular statement applies. 

After the hair is scraped off the hides are treated for the 
removal of lime when this substance has been used as a 



357 

depilatory. This is generally done by steeping in a dilute 
solution of sulphuric acid. In this country hides for heavy 
leather are generally subjected to acid treatment though the 
sweating process has been employed. The acid, if properly 
used, exerts a beneficial action in preparing the skin for 
tanning. The acid is said to plump the fiber. The skins for 
sole leather are generally colored during the plumping. In 
leathers which are required to be soft it is found necessary to 
remove the lime by treating the hide with some putrefactive 
or fermenting bate. This softens the hide by its action on 
the fibrous tissue and abates plumpness. Such bates are 
sour bran, hen's or pigeon's dung. 

Conversion Into Leather. In this country the tanning 
materials used are almost exclusively oak and hemlock 
barks. The greater part is tanned by hemlock. The bark is 
first thoroughly ground and then leached to extract the 
tanning principle from it. The bark liquors are then run 
into the vats, where the hides are packed. The hides are 
successively transferred to vats in which the liquor is 
stronger. In many American tanneries the process is com- 
pleted in from sixty to seventy-five days from the time the 
hides are first subjected to the action of the liquors. 

In England and America the tanning materials are gen- 
erally leached or exhausted and the aqueous extract or decoc- 
tion used in the tanning vats. The operation of tanning is 
thus shortened. 

On the continent of Europe and at many places in this 
country after the hides are subjected to a weak infusion of 
the bark, they are packed in pits with alternate layers of 
bark; the pit is filled with water and the whole left for two 
or three months. The hides are then removed and treated 
in the same way in another pit with fresh bark, the order of 
the hides in the pit being reversed at each transfer. By this 
method the tanning often requires trom ten to fifteen months. 
During tanning the hide increases in weight from 30 to 40 per 



358 

cent. The above description applies to the common heavier 
leathers. Many different tanning materials are used in dif- 
ferent countries and a great variety of leathers produced, of 
these it is here practicable to refer to only a few of the more 
common forms. 

Morocco. The genuine original morocco was made from 
goat skins, but it is now said that an equally good article 
is made from the skin of the hairy seal. Imitation morocco 
is made from sheep-skins. For morocco the depilation is 
by lime and the lime is removed by bate (pigeon's dung). 
The skins are tanned by extract of sumach. They are sewed 
into bags, filled with the tanning liquid and floated in a tank 
of the same. The process is usually complete in twenty- 
four hours. Morocco is generally colored after the tanning 
and the aniline dyes are largely used for this purpose. 

Russian Leather. This form of leather is tanned with 
willow or larch bark. It owes its peculiar odor to the 
essential oil of birch-tar with which it is treated after tan- 
ning. Many imitations of this leather are now made. 

Tawing. Kid. The leather for kid gloves is made from 
the skin of goats and lambs. The skins are unhaired by 
lime and the hair^ removed by sour bran. The tanning is 
accomplished by agitating the skins in a drum containing 
a mixture of flour, alum, salt and yolk of eggs. The alumi- 
num chloride produced prevents putrefaction of the skin 
and the oil and albuminous matters increase softness and 
pliability. This process is called tawing. The kid is col- 
ored after tawing. 

Buckskin; Chamois Leather. These leathers are made 
from the skins of goats, sheep and deer. The skins are 
prepared, limed and bated in the same manner as for mo- 
rocco. They are then thoroughly impregnated with fish, 
whale or other oils by repeated steeping and drying. All 



359 

the water of the hides is thus removed and its place taken 
by oil. The skins are then exposed to a warm atmosphere 
during which some of the oil oxidizes and the skins take a 
yellow color. The excess of oil is then removed by an 
alkaline solution. It is not thought that any chemical 
change occurs in the skin itself, but the fibers are coated 
by the oily products and are very permanent and will not 
yield gelatine with boiling water. Kid does yield gelatine. 
Thicker hides than those above named may be used for this 
leather, but in that case they are made thin by splitting 
and rejecting the grain side. 

Animal Parchment. This parchment is made by the 
mechanical treatment of lamb and goat or other thin skins 
after the hair is removed in the usual way. The skins are 
stretched on frames and rubbed to the necessary thickness 
by sand or pumice stone. 

It is now possible to imitate very closely the natural grain 
of any leather. The thickness desired can also be secured, 
for the modern splitting machines have succeeded in splitting 
a common cow-hide into three and even four layers. By 
these means all the fancy kinds of leather can be imitated. 
Split leather is not so lasting as the natural skin of the same 
thickness, but it is cheaper. The splitting is best done before 
tanning. The skins from which leathers are made are those 
of the ox, horse, sheep, goat, pig, seal, deer and kangaroo. 

PREPARATION OF CHEESE. 

For the better understanding of the process of cheese-making it 
will be well to specify the composition of milk. The milk of all ani- 
mals, both carnivorous and herbivorous, contains about the same 
constituents, though the proportions of the constituents vary con- 
siderably. 

Milk consists essentially of water slightly alkaline, in which are 
dissolved casein, milk sugar and inorganic salts, and in which float 
numerous fatty globules. The fatty matter is the source of butter. 

Good fresh milk is alkaline, its alkalinity is due to soda, which 
holds the casein in solution. If left to itself it soon becomes acid, from 



360 

the formation of lactic acid through the fermentation of the milk 
sugar. Milk is admirably adapted to the nourishment of the animal 
frame. 

CHEESE. 

Cheese is made by coagulating* the milk by the addition of rennet, 
which is part of the stomach of the calf. A piece of rennet is added to 
a large quantity of milk, which is then slowly heated to about 50° C. 
In a short time after this temperature is reached the milk separates 
into a white coagulum or curd, and a slightly yellow translucent liquid 
called whey. The curd contains the casein of the milk, much of the fat 
and some of the inorganic salts. The whey contains the sugar, some 
of the fat and the remainder of the inorganic salts. 

The curd is separated from the whey, well kneaded with some 
common sail and often some coloring substance is added. It is then 
pressed in moulds and set away in an airy and cool place to ripen. 
During the ripening the cheese undergoes a peculiar putrefactive fer- 
mentation, not well understood, by which it acquires its character- 
istic taste and odor. The changes during ripening are brought about 
by the decomposition of the casein and probably of some of the fat. 

The quality of the cheese, of course, depends upon the kind of milk 
employed and the extent to which the ripening is carried. The amount 
of fat largely determines the quality of the cheese, the best qualities 
containing considerable fat. while the poorer are made from skimmed 
milk. The vesicular appearance of certain kinds of cheese is caused by 
the imperfect removal of the whey from the curd. The sugar of the 
whey ferments during the ripening, producing alcohol and carbon 
dioxide: these expanding produce the vesicles. Cheese with less fatty 
matter keeps better than richer cheese. 

From the constituents of cheese it is evident that it possesses con- 
siderable dietetic value. In many places it is an important article of 
daily diet. Cheese cau be made from the milk of any animal, but gen- 
erally comes from the milk of the cow : it is a product of many coun- 
tries. It is largely made in this country and of excellent quality. The 
curd can be separated by adding a little acid to the milk and heating, 
but this is seldom done in cheese-making. 

The successful preparation of artificial butter ( oleo-niargarine) has 
led. in some places, to the use of this substance for the fatty principle 
of cheese, thereby permitting the use of skimmed milk. It is reported 
that this is done to a considerable extent in this country and that 
cotton-seed oil is also here used for the same purpose. 

The red and blue moulds which groAv upon cheese are vegetable 
fungi. The cheese maggot and the cheese mite are animal organisms. 
Cheese like meat may and has been known to undergo decomposition 
with the development of poisonous properties. 



361 

DYEING. 

Dyeing is the art of imparting color to various substances, usually 
textile fabrics, in such manner that it is permanent under the conditions 
to which the fabric is subjected. In dyeing the color penetrates the 
material dyed, which is not the case in painting. 

In order that the dye may penetrate the fabric it is evident that the 
former must be in solution. It is often only necessary to steep the 
fabric in a solution of the coloring matter, the attraction between the 
two imparting a permanent color. In the absence of the necessary 
attraction between the fabric and the dye-stuff, a third substance is 
employed which has an attraction for both ; such substances are called 
mordants. When mordants are used there are usually two steps in the 
operation of dyeing — first, the application of the mordant; second, of 
the coloring matter. The nature of the action between the fabric and 
the mordant and between the fabric and the dye when mordants are 
not used, is not clearly understood. The facts and evidence at present 
seem to indicate that in some cases the action is physical and in others 
that it is chemical. 

In cotton, linen and vegetable substances generally, the action seems 
to be more of a physical one than in the case of silk, wool and other 
animal substances. As a general fact the coloring material permeates 
the latter class more fully than the former, and they may be dyed with 
greater facility and more permanently — the vegetable substances more 
frequently require mordants. The action between the mordant and the 
dye is in most cases a chemical one. 

Mordants. The mordants can generally be classed as acid or basic. 
The principal mordant of the first class is tannic acid. Other vegetable 
acid principles and fatty acids are used for the same purpose. The 
basic mordants comprise a number of metallic salts, the principal of 
which are salts of aluminum, iron, chromium and tin. 

The processes of mordanting cloth are too numerous even for 
present mention. The fibers of the cloth are impregnated with the 
mordanting substance in soluble form and by subsequent treatment it 
is rendered insoluble, if not naturally so after its union with the fiber. 
Usually mordanting precedes dyeing, but sometimes the operations are 
simultaneous and occasionally the dyeing precedes the mordanting. 

Dyestuffs. The chemical character of many of the numerous dye- 
stuffs classes them as either basic or acid. Each of them requires to be 
combined with a mordant of the opposite character to yield a dye. 

We may illustrate the mordanting action by a simple case. If cot- 
ton be steeped in a solution of tannic acid it will absorb it : if it is then 
dipped into a basic coloring matter the acid combines with it ami the 
fiber is dyed. Again, if cotton be steeped in a solution of aluminum 
acetate and then boiled, a basic acetate is deposited in the fiber. If the 



362 

cotton be now dipped into the solution of an acid coloring principle it 
will be permanently dyed. 

Printing. If the dye be applied to only parts of the cloth, so as to 
produce patterns it is called printing. In goods requiring mordants 
this is easily accomplished by mordanting only those parts to be 
printed. Sometimes the cloth is uniformly dyed and the pattern effect 
produced by removing the color from certain parts. This can be done 
by bleaching agents and is known as the discharge method. 



I N DEX 



NUMBERS REFER TO PAGES. 



Acetylene, 98 

preparation, properties, 99 
series, 276 
Acids, basicity, 25 

characteristic property, 25 
how formed, 14 
Affinity, conditions affecting, 19 

defined, 18 
Air, 68 

composition, 69 
Albumins, 306 

egg, 307 
plant, 307 
serum, 307 
Alcoholic beverages, 343 

beer making, 343 
distilled liquors, 
348 
wine making, 345 
Alcohols, 282 

classes, 288 
common, 284 
ethyl, 285 
how derived, 283 
methyl, 283 
propyl, 286 
Alkali metals, 159 
Alkaloids, 308 
Alum, common, 193 
ammonia, 194 
Aluminum, occurrence, 190 
hydroxide, 194 
oxide, 194 [191 

preparation and properties, 
sulphate, 192 
Ammonia, 113 

chemical properties, 115 
preparation, 116 
physical properties, 116 
Ammonium, 174 

acid carbonate, 176 
chloride, 175 
nitrate, 176 
sulphide, 176 
sulphate, 175 
Antimony, 224 
Aqua Regia, 128 
Argon, 158 



Aromatic hydrocarbons, 276 
Arsenic, 155 

acid, 157 
oxide, 155 
sulphides, 157 
Arsenious acid, 157 
Atmosphere, 68 

composition, 69 
Atomic theory, Dalton's, 9 
Atomic weights, 28 

determination by an- 
alysis, 29 
determination by Avo- 

gadro's law, 35 
determination by de- 
composition, 31 
determination by sub- 
stitution, 30 
Atoms, number in molecule, 39 

Balsams, 279 
Barium, 177 

carbonate, 177 

chlorate, 178 

chloride, 177 

hydroxide, 178 

nitrate, 178 

properties of salts, 178 

sulphide, 178 

sulphate, 177 
Bellite, 334 
Bases, 23 

Basic anhydrides, 24 
Benzene, 273 

series, 276 
Binary compounds, 13 
Bismuth, 223 
Borates, 113 
Boric acid, 112 
Boron, 112 
Bread making, 348 

fermented, 349 
unfermented, 350 
Bromine, 108 

preparation, properties. 129 

Caffeine, 308 

Calcium, 178 



364 



Calcium, carbonate, 179 
chloride, 183 
fluoride, 183 
hydroxide, 180 
salts, reactions of, 183 
sulphide, 183 
sulphate, 182 
sulphate, hydrous, 182 
Calorific intensity, 312 

power or value, 311 
Camphors, 278 
Candle flame, 103 
Carbon, 73 

animal charcoal, 88 
chemical properties, 89 
coke, 88 

common charcoal, 85 
diamond, 83 
, graphite, 84 
lampblack, 84 
Carbon compounds, 267 
Carbon dioxide, 90 

chemical properties, 92 
physical properties, 91 
preparation, 94 
Carbonic acid and its salts, 94 
Carbon monoxide, 95 
Carborundum, 112 
Casein, 307 
Catalytic action, 20 
Caoutchouc, 279 
Celluloid, 333 
Cerium, 227 

Cheese, preparation, 359 
Chemistry, definition, 6 
Chlorine/ 122 

oxygen compounds, 128 
-preparation, properties, 123 
uses, 124 
Chromium, 222 
Cobalt, 220 
Cocaine, 309 
Coke, 88 

Collodion cotton, 332 
Colors, vegetable, 305 
Copper, 237 ' 

carbonate, 245 
oxides, 244 
properties, 243 
sulphate, 244 
uses, 244 
Copper, dry reduction, 237 

concentration of native, 238 
oxides, 238 
sulphides, 239 
Copper, extract'n of precious metals, 242 
electrolytic method, 242 
liquation process, 243 



Copper, Ziervogel's method, 243 
Copper, smelting without fuel, 241 
Copper, wet reduction, 241 

Davy's lamp, 108 
Diamond, 83 
Disposing affinity, 21 
Dissociation, 21 
Di-sulphuric acid, 148 
Dynamite, 330 

Elements, definition, 5 

table, 7 
Equivalent weights, 27 
Ethene, 98 
Ethvl alcohol, 285 
Ethylene, 99 
Explosives, 332 

compounds, 327 

mixtures, 324 

Fats, fixed oils, 352 
Ferments, 284 
Ferro-manganese, 222 
Fibrin, 307 
Fire wire, 322 
Flame, 100 

blowpipe, 106 

candle, 103 

hydrocarbon, 103 

lighting, 104 

luminosity, 101 

oxy-hydrogen, 107 

structure, 102 
Fluorine, 131 

preparation, properties, 132 
Formulae, constitutional, 270 
rational, 270, 
structural, 270 
to determine, 53 
Furnace, iron, 197 

Gas, illuminating, 337 
manufacture, 339 
secondary products, 342 
water, 96 
Gelatine, 306 
Gelatine dynamite, 333 
Gelatine explosives, 332 
Gelignite, 333 
Germanium, 227 
Glass, 314 

Bohemian, 316 

crown, 315 

devitrified, 318 

flint, lead, 316 

plate, 315 

pressed, 317 

production, 316 

window, 315 



365 



Glue, 307 
Gluten, 307 
Glycerides, fats, 352 
Glycerine, 286 

preparation, properties, 277 
Gold, 260 

chloride, oxide, sulphide, 266 

properties, 266 

metallurgy, 260 

African extraction, 265 

amalgamation, 262 

chlorination, 263 

chlorine leaching, 263 

cyanide leaching, 263 

extraction from vein quartz, 261 

extraction from sedimentary de- 
posits, 264 

extraction by smelting, 261 
Graphite, 84 
Gutta percha, 282 
Gun cotton, 331 
Gunpowder, 325 

Helium, 158 
Hydracids, 6 
Hydrocarbons, 271 

aromatic, 276 
saturated, 272 
unsaturated, 275 
Hydrobromic acid, 129 
Hydrochloric acid, 125 
Hydrofluoric acid, 132 
Hydrogen, 62 

chemical properties, 64 
heat of combustion, 65 
peroxide, 82 
preparation, 66 
physical properties, 63 
reducing power, 66 
Hydrogen sulphide, 136 

action with metals 
and oxides, 137 
action with metal- 
lic salts, 138 
preparation, 139 
properties, 137 
Hydrozine, 117 
Hyposulphurous acid, 149 

India rubber, 279 

applications to fabrics, 281 
vulcanized, 280 
Indigo, 305 
Iodine, 130 

compounds, uses 131 
Iron, 195 

carbonate, 219 



Iron, chemical properties, 217 
oxides, 218 
reaction of salts, 220 
sulphate, 219 
sulphides, 219 
Iron, cast, 196 

composition, 203 
fuel for reduction, 198 
furnace, 197 

furnace gases, 202 [ores, 197 
preliminary treatment of 
reduction from ores, 198 
slag and fluxes, 201 
uses of slag, 202 
Iron, wrought, manufacture, 206 
Eames process, 209 
properties of bar iron, 210 
puddling, mechanical, 208 
puddling, manual, 206 
Isinglass, 306 
Isomerism, 271 
Isomorphism, 41 

Kerosene, 274 

Lamps, safety, 107 
Davy's, 108 
Stephenson's, 109 
Laughing gas, 121 
Law, Avogadro's, 32 

definite proportions, 8 
even numbers, 48 
insolubility, 19 
multiples, 9 
periodicity, 51 
Pettit and Dul 
volatility, 19 
volumes, 42 
Lead, desilverizing, 230 
cupellation, 232 
Parke's process, 231 
Pattinson's process, 232 
occurrence, 227 
carbonates, 235 
oxides, 236 
Lead, reduction, 227 [method, 229 
American wester n 
other processes, 228 
Leather manufacture, 355 
buckskin, 358 
kid, 358 
morocco, 358 
Russian. 358 
Legumin, 307 

Magnseium, 184 [ide. sulphate. 185 
carbonate, chloride. ox- 
Manganese, 222 



366 



Marsh gas, methane, 97 

properties, 98 
Mercury, 252 

chlorides, oxides, 256 
metallurgy, 253 
sulphides, 255 
properties, uses, 256 
Molecular weights, 32 [law, 32 

from Avogadro's 
by other means, 34 
Molecule, definition, 11 

unsaturated, 49 
Molybdenum, 223 
Morphine, 308 

Naphtha, 273, 

Nascent state, 20 
Nickel, 221 
Nicotine, 308 
Niobium, 224 
Nitrates, 121 
Nitric acid, 118 

properties, 119 
oxide, 122 
Nitro-compounds, 333 [334 

Nitro-compounds and organic nitrates, 
Nitrogen, 67 

oxides, 118 
pentoxide, 122 
preparation, 68 
tetroxide, 122 
Nitro-glycerine, 328 

derivatives, 330 
Nitro-muriatic acid, 128 
Nitrous anhydride, 122 

oxide laughing gas, 121 
Nomenclature, 13 

prefixes, 14 
suffixes, 15 
Notation, 11 

Olefiant gas, 99 
Olefine series, 275 
Opium, 308 

Organic chemistrv, 267 
Oxides, 13 
Oxygen, 57 

action on metals, 59 

non-metals, 58 

preparation, 60 

properties, 57 
Ozone, 61 

Paraffin series, 272 
Petroleum, 273 
Phosphorus, 150 

amorphous, 153 

common. 152 



Phosphorus, compounds of, 155 
oxy-acids of, 154 
pentoxide, 154 
preparation, 152 
uses, 154 
Picric acid, tri-nitro-phenol, 334 
Platinum, 257 

compounds, 259 
related metals, 259 
Potassium. 159 

bicarbonate, 162 
bromide, 163 
chlorate, 165 
chloride, 163 
hydroxide, 162 
nitrate, 163 

oxides and sulphides, 166 
sulphate, 166 
Potassium carbonate, 161 

from ashes, 161 
from beet-root, 
161 
from chloride, 

162 
from sheep's 

wool, 162 

properties, etc., 

Potterv, 318 [162 

kilns, 321 
Polvmerism, 271 
Porcelain, 319 

Pressure, influence on chemical action, 
Pyro-sulphuric acid, 148 [21 

Quinine, 309 

PiACK-A-ROCK, 234 

Radicals, 22 
Resins, 278 

Selenium, 149 
Silica, 110 
Silicon, 111 
Silver, 245 

chloride, nitrate, 251 

properties, uses, 249 

reaction of salts, 252 
Silver, reduction from ores, 245 

amalgamation process, 246 

leaching process, 248 

smelting for, 245 
Smokeless powders, 335 
Soap making, 353 
Soda, caustic, 172 
Sodium, 166 

bicarbonate, 170 
chloride, 168 



367 



Sodium, borate, 173 

hydroxide, 172 
manufacture, 167 
nitrate, 173 
silicate, sulphate, 173 
thiosulphite, 173 
Sodium carbonate, manufacture, 170 
Leblanc process, 170 
Salvay process, 171 
properties, 171 
Spiegeleisen, 222 
Steel, manufacture, 210 

cementation process, 213 
crucible steel, 215 
Bessemer process, acid, 211 

basic, 212 
open hearth, 212 
compared with iron, 216 
Stochiometry, 52 
Stoneware, 320 
Sulphates, 147 
Sulphur, 133 

chemical properties, 135 
dioxide, 140 

extraction, native, 133 [135 
extraction from sulphides, 
physical properties, 136 
trioxide, 142 
Sulphuric acid, 142 

di-sulphuric, 148 
manufacture, 143 
properties, 146 
Strychnine, 309 

Tantalum, 224 

Tellurium, 150 
Terpenes, 277 
Thallium, 195 



Theine, 308 

Thiosulphuric acid, 149 
Thorium, titanium, 227 
Tin, 224 

alloys, 226 

oxides, salts, 227 

reduction, 225 
Tungsten, 222 
Turpentine, 277 

Uranium, 223 

Valency, 47 

variable, 50 
Vanadium, 224 
Vegetable colors, 305 
Vulcanite, 281 

Water, 71 

chemical properties, 75 
physical properties, 71 
solvent powers, 74 
of crystallization, 73 
Waters, natural, 76 

action on soap, 80 
deposits from, 79 
hard and soft, 78 
mineral, 81 
purification of, 81 
river and sea, 81 

Xylonite, 333 

*Zinc, 186 

chloride, oxide, sulphate, 189 
reactions of salts, 190 
uses, 188 
Zirconium, 227 



fc ^F 







